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Equations/302419: 14.Solve using the five-step problem-solving process. Show all steps necessary to arrive at your solution.
You are putting a stone border of uniform width around a rectangular garden that measures 6 yards by 15 yards. You only have enough stone to cover 100 square yards. How wide should the border be?

1 solutions

Answer 216825 by josmiceli(9817) About Me  on 2010-05-09 18:44:36 (Show Source):
You can put this solution on YOUR website!
I'm not familiar with the 5-step process, but I
can show you how I'd do it
Let x = the width of the border
The area of the garden is 6%2A15+=+90 yd2
The dimensions of the garden + border are:
6+%2B+2x by 15+%2B+2x
The area of the garden + border is
A+=+%286+%2B+2x%29%2A%2815+%2B+2x%29
The area of the garden is 6%2A15+=+90 yd2
The area of the border is 100 yd2
A+=+190
190+=+%286+%2B+2x%29%2A%2815+%2B+2x%29
190+=+90+%2B+30x+%2B+12x+%2B+4x%5E2
4x%5E2+%2B+42x+-+100+=+0
Solve using quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a+=+4
b+=+42
c+=+-100
x+=+%28-42+%2B-+sqrt%28+42%5E2-4%2A4%2A%28-100%29+%29%29%2F%282%2A4%29+
x+=+%28-42+%2B-+sqrt%28+1764+%2B+1600+%29%29%2F8+
x+=+%28-42+%2B-+sqrt%28+3364+%29%29%2F8+
x+=+%28-42+%2B+58%29%2F8 (there's another solution, but it's negative)
x+=+2
The border around the garden is 2 yds wide
check:
190+=+%286+%2B+2x%29%2A%2815+%2B+2x%29
190+=+%286+%2B+4%29%2A%2815+%2B+4%29
190+=+10%2A19
190+=+190
OK


Finance/302052: I need help with this impossible problem
Jake has 6 coins.
Ellie has 12 coins.
There is a total of 5 quarters.
Jake has more than $1
Jake's coins are worth three times as much as Ellie's coins.
How much money does Jake have?
How much money does Ellie have?
My niece's teacher apparently wants us to show our work (my niece is in the 2nd grade and she somehow has this problem for a test. she's failing most of her tests and I want to find out why.) There is supposed to be a non-algebraic way to solve this problem since she is only in the 2nd grade. I hope you can reply soon.
1 solutions

Answer 216594 by josmiceli(9817) About Me  on 2010-05-08 17:08:27 (Show Source):
You can put this solution on YOUR website!
2nd grade? I was taking remedial sandbox and advanced crayons.
This is a problem where she has to come to some logical
conclusions and put them together to get what they're
looking for
They don't say anything about it, but any number of pennies, nickels,
and dimes may be used
I focused on "Jake has more than $1"
(case #1) Jake could have 3 quarters and 3 dimes, giving him $1.05
(case #2) or, he could have 4 quarters, and it doesn't matter what the other 2 coins are
(case #3) 0r, he could have 5 quarters, and it doesn't matter what the other coin is
Now I look at "Jake's coins are worth 3 times Ellie's coins"
So, Jakes coins must be evenly divisible by 3
for case #1: 1.05/3 = .35
So, if Ellie has 12 coins, and I know 2 of them are quarters, she's already got
$.50, so case #1 doesn't work
for case #2: Jake could have:
$1.20 (4 quarters and 2 dimes)
$1.10 (4 quarters and 2 nickels)
$1.15 (4 quarters , a nickel and a dime)
$1.11 (4 quarters, a dime and a penny)
$1.06 (4 quarters, a nickel, and a penny)
$1.02 (4 quarters and 2 pennies)
The right one has to be evenly divisible by 3
$1.20/3 = .40
$1.11/3 = .37
$1.02/3 = .34
Now Ellie has 1 quarter, so her 11 remaining coins must add up to
.40 - .25 = .15
or
.37 - .25 = .12
or
.34 - .25 = .09
There's no way to get the last 2 with 11 coins, but
.15 = 10 pennies and a nickel
So, she ends up with 1 quarter, 10 pennies, and 1 nickel
when Jake has 4 quarters and 2 dimes
Now I just have to deal with case #3
Jake has either:
5 quarters and a dime = $1.35
5 quarters and a nickel = $1.30
5 quarters and a penny = $1.26
$1.35/3 = .45
$1.26/3 = .42
Nellie has 12 coins to make $.45
That would be 5 pennies, 6 nickels, and 1 dime
I can't seem to make $.42 with 12 coin, but no quarters
So, what I finally come up with is:
--------------------------------
When Jake has 4 quarters and 2 dimes,
Nellie has 1 quarter 1 nickel, 10 pennies
---------------------------------
When Jake has 5 quarters and 1 dime,
Nellie has 1 dime, 6 nickels, and 5 pennies
---------------------------------
Whew! What grade is she in?
This was hard for me. I'm still not sure I've
got all the answers and I've got 2 years of college


Travel_Word_Problems/302051: How long will it take for a car to travel 14 miles if it travels at a constant speed of 45 miles per hour?
1 solutions

Answer 216582 by josmiceli(9817) About Me  on 2010-05-08 15:55:29 (Show Source):
You can put this solution on YOUR website!
How long does it take to go 1 mile?
d+=+r%2At
1+=+45%2At
t+=+1%2F45 hr
It will take 14 times longer to go 14 miles
t+=+14%2F45 hr


Probability-and-statistics/302030: The Everton College store paid $1755 for an order of 49 calculators. The store paid $8 for each scientific calculator. The others, all graphing calculators, cost the store $55 each. How many of each type of calculator was ordered?
1 solutions

Answer 216581 by josmiceli(9817) About Me  on 2010-05-08 15:48:11 (Show Source):
You can put this solution on YOUR website!
Let x = number of graphing calculators bought
49+-+x = number of scientific calculators bought
8%2A%2849+-+x%29+%2B+55x+=+1755
392+-+8x+%2B+55x+=+1755
47x+=+1363
x+=+29
49+-+x+=+20
20 scientific and 29 graphing were bought
check:
8%2A%2849+-+x%29+%2B+55x+=+1755
8%2A%2849+-+29%29+%2B+55%2A29+=+1755
160+%2B+1595+=+1755
1755+=+1755
OK


logarithm/302047: find the value of y.
log4 64=y
1 solutions

Answer 216580 by josmiceli(9817) About Me  on 2010-05-08 15:39:05 (Show Source):


Linear-equations/302040: Here's another accuplacer practice question that I have no clue about: "write the slope intercept form of the equation (-2,0)and (7,4). The answer that lights up correct is Y=4/9x + 8/9. Can someone tell me why this is correct, and in general , how to write slope intercept forms? Thanks lots.
1 solutions

Answer 216578 by josmiceli(9817) About Me  on 2010-05-08 15:36:30 (Show Source):
You can put this solution on YOUR website!
The formula to use when given 2 points is:

where the given points are:
(x1,y1) and (x2,y2)
It doesn't matter which is which, but I can call
(x1,y1) = (-2,0)
and
(x2,y2) = (7,4)
Putting these into the formula:
%28y+-+4%29%2F%28x+-+7%29+=+%280+-+4%29%2F%28-2+-+7%29
%28y+-+4%29%2F%28x+-7%29+=+4%2F9
Multiply both sides by x-7
y+-+4+=+%284%2F9%29%2A%28x+-+7%29
y+-+4+=+%281%2F9%29%2A%284x+-+28%29
9y+-+36+=+4x+-+28
9y+=+4x+%2B+8
y+=+%284%2F9%29%2Ax+%2B+8%2F9 answer


absolute-value/302032: Solve and write using interval notation: -3 < -5x + 7 <= 8

1 solutions

Answer 216575 by josmiceli(9817) About Me  on 2010-05-08 15:20:48 (Show Source):
You can put this solution on YOUR website!
-3+%3C+-5x+%2B+7+%3C=+8
This says 2 things:
(1) -3+%3C+-5x+%2B+7
and
(2) -5x+%2B+7+%3C=+8
Subtract 7 from both sides of (1)
(1) -3+-7+%3C+-5x
(1) -10+%3C+-5x
Divide both sides by -5 and reverse < sign
(1) 2+%3E+x
or,
(1) x+%3C+2
Now subtract 7 from both sides of (2)
-5x+%3C=+1
Divide both sides by -5 and reverse sign
x+%3E=+-1%2F5
Or, what is the same thing:
-1%2F5+%3C=+x
Putting (1) and (2) together:
-1%2F5+%3C=+x+%3C+2 answer


logarithm/301760: how to rewrite log(1000) in the terms of log(2)and log(5?
1 solutions

Answer 216440 by josmiceli(9817) About Me  on 2010-05-07 21:33:55 (Show Source):


Linear_Equations_And_Systems_Word_Problems/301785: approximately one half of all glass bottles distributed will be recycled each year. A beverage company distributes 310,000 bottles. the number in use after t
years is given by the function. N(t)=310,000(1/2)^t.
How many years will 5000 bottles still be in use?
I've tried several different ways to work this function and get a different answer every time!!!!!! Do Ineed to replace N for the 5000 to solve?
Thanks,
Desperately Trying
1 solutions

Answer 216438 by josmiceli(9817) About Me  on 2010-05-07 21:26:54 (Show Source):
You can put this solution on YOUR website!
N%28t%29+=+310000%2A%281%2F2%29%5Et
5000+=+310000%2A%281%2F2%29%5Et
Multiply both sides by 2%5Et
2%5Et+=+310000%2F5000
2%5Et+=+62
take the log of both sides
log%282%5Et%29+=+log%2862%29
t%2Alog%282%29+=+log%2862%29
t+=+log%2862%29%2Flog%282%29
You can solve with calculator


Travel_Word_Problems/301797: A helicopter goes 720 miles with the wind in the same time it can go 630 miles against
the wind. The speed of the wind is 6 miles per hour. Find the speed of the helicopter
with no wind.
1 solutions

Answer 216434 by josmiceli(9817) About Me  on 2010-05-07 21:15:22 (Show Source):
You can put this solution on YOUR website!
Let h = speed of helicopter with no wind
6 = speed of wind
given:
with the wind:
720+=+%28h+%2B+6%29%2At
against the wind:
630+=+%28h+-+6%29%2At
---------------
This is 2 equations with 2 unknowns
solve for h and t


Expressions-with-variables/301808: You have 6 trucks and 5 cars. Each truck pays twice as much as each car to use the toll. At the end of the day $12.75 was collected. Write the algebraic equation and solve the problem.
1 solutions

Answer 216430 by josmiceli(9817) About Me  on 2010-05-07 21:08:56 (Show Source):
You can put this solution on YOUR website!
Let c = toll for 1 car
Let t = toll for 1 truck
given:
t+=+2c
6t+%2B+5c+=+12.75
6%2A%282c%29+%2B+5c+=+12.75
12c+%2B+5c+=+12.75
17c+=+12.75
solve for c, then t


Miscellaneous_Word_Problems/301827: A 60% acid solution is to be mixed with a 80% acid solution to produce 20 liters of a 65% acid solution. How many liters of each solution is needed? I tried setting up a table but that didn't work. Can you please explain how you derive at your answer. Thanks and have a wonderful weekend.
1 solutions

Answer 216424 by josmiceli(9817) About Me  on 2010-05-07 20:58:41 (Show Source):
You can put this solution on YOUR website!
Let a = liters of 60% solution needed
Let b = liters of 80% solution needed
given:
.6a = acid in 60% solution
.8b = acid in 80% solution
-----------------------
(1) a+%2B+b+=+20 liters
%28.6a+%2B+.8b%29%2F20+=+.65
.6a+%2B+.8b+=+13
(2) 6a+%2B+8b+=+130
Multiply both sides of (1) by 6 and
subtract from (2)
(2) 6a+%2B+8b+=+130
(1) +-6a+-+6b+=+-120
2b+=+10
b+=+5
a+=+15
15 liters of 60% solution and 5 liters of 80% solution are needed


Volume/301653: On her early morning walk, Jinhee noticed that when she walked under a streetlight, her shadow would get longer the farther she was away from the light. She decided to use her shadow to find out how tall the light was. When she was 21 feet from the base of the light, her shadow was 7 feet long. She is 5 feet 6 inches
1 solutions

Answer 216281 by josmiceli(9817) About Me  on 2010-05-07 09:28:17 (Show Source):
You can put this solution on YOUR website!
There are 2 similar right triangles:
One is formed by her and her shadow
The other is formed by the streetlight
and (distance to her + her shadow)
I can write a ratio of the sides
of these similar triangles:
Let x = the height of the streetlight
5.5%2F7+=+x%2F%2821+%2B+7%29
5.5%2F7+=+x%2F28
multiply both sides by 28
4%2A5.5+=+x
x+=+22
The streetlight is 22 ft high


Mixture_Word_Problems/301657: A chemist has some 8% hydrogen peroxide solution and some 3% hydrogen peroxide solution, how many milliliters of each should be used to make 500-milliliter solution that is 4%?
1 solutions

Answer 216277 by josmiceli(9817) About Me  on 2010-05-07 09:20:11 (Show Source):
You can put this solution on YOUR website!
Let a = ml of 8% solution needed
Let b = ml of 3% solution needed
given:
hydrogen peroxide in 8% solution:
.8a ml
hydrogen peroxide in 3% solution:
.3b ml
-----------------
%28.08a+%2B+.03b%29%2F500+=+.04
.08a+%2B+.03b+=+.04%2A500
.08a+%2B+.03b+=+20
(1) 8a+%2B+3b+=+2000
and
(2) a+%2B+b+=+500
Multiply both sides of (2) by 3
and subtract (2) from (1)
(1) 8a+%2B+3b+=+2000
(2) -3a+-+3b+=+-1500
5a+=+500
a+=+100
and, since
a+%2B+b+=+500
100+%2B+b+=+500
b+=+400
100 ml of 8% solution and 400 ml of 3% solution are needed
check:
.08a+%2B+.03b+=+20
.08%2A100+%2B+.03%2A400+=+20
8+%2B+12+=+20
20+=+20
OK



Linear-equations/301601: how many liters of sprite must be added to 8 liters of a mixture of 30% sprite and 70% lime juice to obtain a mixture which is 40% sprite and 60% lime juice. All percentages are by volume
1 solutions

Answer 216256 by josmiceli(9817) About Me  on 2010-05-07 00:42:13 (Show Source):
You can put this solution on YOUR website!
There are 8 liters of a mixture of 30% sprite and 70% lime juice
The liters of sprite is:
.3%2A8+=+2.4
The liters of lime juice is:
.7%2A8+=+5.6
Call the liters of sprite added to this to get 40% sprite x
%282.4+%2B+x%29%2F%288+%2B+x%29+=+.4
2.4+%2B+x+=+.4%2A%288+%2B+x%29
2.4+%2B+x+=+3.2+%2B+.4x
.6x+=+.8
x+=+4%2F3 liters
4/3 liters of sprite must be added
check:
The % of lime juice is:
5.6%2F%288+%2B+4%2F3%29+=+.6
5.6+=+.6%2A%2828%2F3%29
5.6%2A3+=+.6%2A28
16.8+=+16.8
OK


Travel_Word_Problems/301604: Two cars leave an intersection. One car travels east; the other north. When the car traveling east had gone 15 miles, the distance between the cars was 5 miles more than the distance traveled by the car heading north. How far had the northbound car traveled?

1 solutions

Answer 216252 by josmiceli(9817) About Me  on 2010-05-07 00:25:58 (Show Source):
You can put this solution on YOUR website!
The 2 cars and their starting point form a right triangle
One leg is 15 mi
Call the north leg x
Then the distance between the cars is 5+%2B+x
x%5E2+%2B+15%5E2+=+%28x%2B5%29%5E2
x%5E2+%2B+225+=+x%5E2+%2B+10x+%2B+25
10x+=+225+-+25
10x+=+200
x+=+20
The northbound car had gone 20 mi
check:
x%5E2+%2B+15%5E2+=+%28x%2B5%29%5E2
20%5E2+%2B+15%5E2+=+%2820%2B5%29%5E2
400+%2B+225+=+625
625+=+625
OK


Linear-equations/301416: How would I graph c=30t+20? and also Media services charge $20 for a phone and $30/month for the economy plan, the equation c=30t+20 describes the total cost, c, of operating a media services phone for t months.what is total cost for 3 months of service? and also if a customer has $90 how many months of services can they get? Thanks so much
1 solutions

Answer 216196 by josmiceli(9817) About Me  on 2010-05-06 20:27:51 (Show Source):
You can put this solution on YOUR website!
Plot c on the vertical axis, and t on
the horizontal axis
You plot it by plugging values of t into the equation
and finding c, like
t+=+1
c+=+50
Here's the plot:
+graph%28+400%2C+400%2C+-2%2C+6%2C+-5%2C+120%2C+30x+%2B+20%29+


Radicals/301512: 3 square root 12 + 4 square root3
1 solutions

Answer 216191 by josmiceli(9817) About Me  on 2010-05-06 20:19:02 (Show Source):


logarithm/301411: write -2logx-3logy+logz as one logarithm.
1 solutions

Answer 216189 by josmiceli(9817) About Me  on 2010-05-06 20:14:00 (Show Source):


Travel_Word_Problems/301440: If you drive at 80 mph, how long would it take to drive 118 miles?
1 solutions

Answer 216188 by josmiceli(9817) About Me  on 2010-05-06 20:07:23 (Show Source):
You can put this solution on YOUR website!
How long does it take to drive 1 mi?
d+=+r%2At
t+=+d%2Fr
t+=+1%2F80hr
It takes 118 times as long to drive 118 mi
%281%2F80%29%2A118+=+1.475 hr


logarithm/301459: What expression is equivalent to log(base 7)2401-log(base 3)243?
1 solutions

Answer 216185 by josmiceli(9817) About Me  on 2010-05-06 20:00:29 (Show Source):
You can put this solution on YOUR website!
Playing with my calculator, I found that
2401+=+7%5E4
log%287%2C+7%5E4%29+=+4
And I found that
243+=+3%5E5
log%283%2C3%5E5%29+=+5
so,
log%287%2C2401%29+-+log%283%2C243%29+=+4+-+5
4+-+5+=+-1 answer


percentage/301358: A 60% acid solution is to be mixed with a
80% acid solution to produce 20 Liters of a
65% acid solution. How many liters of each
solution is needed?
1 solutions

Answer 216058 by josmiceli(9817) About Me  on 2010-05-06 13:25:23 (Show Source):
You can put this solution on YOUR website!
Let a = liters of 60% solution needed
Let b = liters of 80% solution needed
given:
(1) a+%2B+b+=+20 liters
.6a+%2B+.8b+=+.65%2A20
.6a+%2B+.8b+=+13
(2) 6a+%2B+8b+=+130
Multiply both sides of (1) by 6 and subtract (1) from (2)
6a+%2B+8b+=+130
-6a+-+6b+=+-120
2b+=+10
b+=+5
and, since
a+%2B+b+=+20
a+%2B+5+=+20
a+=+15
15 liters of 60% solution and 5 liters of 80% solution are needed
check:
In words:
(liters of acid you end up with) / (final total liters of solution) = 65%
%28.6%2A15+%2B+.8%2A5%29%2F20+=+.65
9+%2B+4+=+.65%2A20
13+=+13
OK


Money_Word_Problems/300978: I need help with this word math problem.
In a collection of nickels, dimes, and quarters, there are twice as many dimes as nickels, and fewer quarters than dimes. If the total value of the coins is $4.50, how many of each type of coin are there?
1 solutions

Answer 215858 by josmiceli(9817) About Me  on 2010-05-05 17:51:50 (Show Source):
You can put this solution on YOUR website!
Let n = number of nickels
Let d = number of dimes
Let q = number of quarters
given:
5n+%2B+10d+%2B+25q+=+450 (in cents)
d+=+2n
q+%3C+d
---------
By substitution:
5n+%2B+10%2A%282n%29+%2B+25q+=+450
25n+%2B+25q+=+450
n+%2B+q+=+18
d%2F2+%2B+q+=+18
I know that q%3C18, since quarters must add up to less than $4.50
If q%3Cd then, suppose q+=+11, d could be 10
That's $2.75 plus $1.00 = $3.75. If there are twice as many dimes as
nickels, n+=+5, totaling $.25
$3.75 + $.25 = $4.00
My next guess is q+=+13,d+=+12, n+=+6
You can go on from here, since you get the idea


Radicals/300965: Please help me solve (2 radical 2)squared. I came up with the answer 4, as did the calculator but the book says the answer is 8. Can you show me how to solve this with the steps please? Thanks in advance!
1 solutions

Answer 215849 by josmiceli(9817) About Me  on 2010-05-05 17:31:44 (Show Source):
You can put this solution on YOUR website!
You can break it up like this:
%282%2Asqrt%282%29%29%5E2+=+2%5E2+%2A+%28sqrt%282%29%29%5E2
2%5E2%2A%28sqrt%282%29%29%5E2+=+4%2A2
4%2A2+=+8


Percentage-and-ratio-word-problems/300960: a stock decreases in value by 20 percent by what percent must the stock price increase to reach its former value?
1 solutions

Answer 215845 by josmiceli(9817) About Me  on 2010-05-05 17:21:44 (Show Source):
You can put this solution on YOUR website!
Let v = stock's original value
.8v = stock's value minus 20%
Let x%2F100 = percent that it must increase
given:
%28x%2F100%29%2A%28.8v%29+%2B+.8v+=+v
.8v%2A%28x%2F100+%2B+1%29+=+v
---------------
x%2F100+%2B+1+=+1%2F.8
x%2F100+=+1%2F.8+-+1
x%2F100+=+1.25+-+1
x+=+100%2A.25
x+=+25
The stock must increase by 25%


Quadratic-relations-and-conic-sections/300963: Parabala...Word problem: What are the 3 consecative intragals numbers that sum 117?
1 solutions

Answer 215844 by josmiceli(9817) About Me  on 2010-05-05 17:04:49 (Show Source):
You can put this solution on YOUR website!
To correct your spelling:
What are the 3 consecutive integer numbers that sum 117?
Call the consecutive numbers n, n%2B1, and n%2B2
given:
n+%2B+n+%2B+1%2B+n+%2B+2+=+117
3n+%2B+3+=+117
3n+=+114
n+=+38
n+%2B+1+=+39
n+%2B+2+=+40
The numbers are 38, 39, and 40
check:
38+%2B+39+%2B+40+=+117
117+=+117
OK


Quadratic_Equations/299958: The cost of 5 boxes of cookies is 15 dollars. Which equation shows this in function notation?
1 solutions

Answer 215385 by josmiceli(9817) About Me  on 2010-05-03 17:01:46 (Show Source):
You can put this solution on YOUR website!
First find the cost of 1 box
15%2F5+=+3 dollars/box
Let x = number of boxes
f%28x%29 = cost of x boxes
f%28x%29+=+15%2A%28x%2F5%29
f%28x%29+=+3x


Graphs/299969: Use the quadratic formula to determine the x-intercepts (if any) of the following function. Then evaluate the function for several values of x, and use the resulting points to graph the function. Show your work.
f(x) = 3x^2
1 solutions

Answer 215382 by josmiceli(9817) About Me  on 2010-05-03 16:52:22 (Show Source):
You can put this solution on YOUR website!
x-intercepts occur where f%28x%29+=+0
The quadratic equation is
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
when the equation is in the form
f%28x%29+=+ax%5E2+%2B+bx+%2B+c
a+=+3
b+=+0
c+=+0
x+=+%28-0+%2B-+sqrt%28+0%5E2-4%2A3%2A0+%29%29%2F%282%2A3%29+
x+=+sqrt%280%2F6%29
x+=+0
The only x-intercept is at x+=+0


Linear-equations/299962: What is the slope intercept form of a line that passes through point (0,2) and is parallel to the graph of y=-3x-6?
1 solutions

Answer 215375 by josmiceli(9817) About Me  on 2010-05-03 16:41:51 (Show Source):
You can put this solution on YOUR website!
The equation y+=+-3x+-+6 is in the form
y+=+mx+%2B+b where m is the slope, so
m+=+-3
Any line parallel to this line will also have m+=+-3
I can write this equation as
y+=+-3x+%2B+b
To find b, I just plug in the (x,y) = (0,2)
2+=+-3%2A0+%2B+b
b+=+2
So, the equation is
y+=+-3x+%2B+2


Travel_Word_Problems/299982:
A motorboat takes 4 hours to travel 320 mi going upstream. The return trip takes hours 2 going downstream. What is the rate of the boat in still water and what is the rate of the current?
1 solutions

Answer 215370 by josmiceli(9817) About Me  on 2010-05-03 16:35:27 (Show Source):
You can put this solution on YOUR website!
Let r%5Bs%5D = rate of boat in still water
Let r%5Bc%5D = rate of the current
Write 2 equations, one for upstream and one for downstream
given:
t%5Bu%5D+=+4 hrs
t%5Bd%5D+=+2 hrs
d=+320 mi
-----------
upstream:
d+=+r%5Bu%5D%2At%5Bu%5D
d+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2At%5Bu%5D
(1) 320+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2A4
downstream:
d+=+r%5Bd%5D%2At%5Bd%5D
d+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2At%5Bd%5D
(2) 320+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2A2
-----------------
(1) r%5Bs%5D+-+r%5Bc%5D+=+80
(2) r%5Bs%5D+%2B+r%5Bc%5D+=+160
Add the equations
2r%5Bs%5D+=+240
r%5Bs%5D+=+120 mi/hr
And, since
(1) r%5Bs%5D+-+r%5Bc%5D+=+80
120+-+r%5Bc%5D+=+80
r%5Bc%5D+=+40 mi/hr
The rate of the boat in still water is120 mi/hr
The rate of the current is 40 mi/hr
check:
(1) 320+=+%28r%5Bs%5D+-+r%5Bc%5D%29%2A4
320+=+%28120+-+40%29%2A4
320+=+320
and
(2) 320+=+%28r%5Bs%5D+%2B+r%5Bc%5D%29%2A2
320+=+%28120+%2B+40%29%2A2
320+=+320
OK


Problems-with-consecutive-odd-even-integers/299768: Factor completely. Show all work
7x2 + 11x – 30
1 solutions

Answer 215293 by josmiceli(9817) About Me  on 2010-05-03 10:23:28 (Show Source):
You can put this solution on YOUR website!
7x%5E2+%2B+11x+-+30
Use the quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a+=+7
b+=+11
c+=+-30
x+=+%28-11+%2B-+sqrt%28+11%5E2-4%2A7%2A%28-30%29+%29%29%2F%282%2A7%29+
x+=+%28-11+%2B-+sqrt%28+121+%2B+840+%29%29%2F14+
x+=+%28-11+%2B-+sqrt%28961%29%29%2F14+
x+=+%28-11+%2B+31%29%2F14
x+=+20%2F14
x+=+10%2F7
and, also
x+=+%28-11+-+31%29%2F14
x+=+-42%2F14
x+=+-3
The factors are:
%28x+-+10%2F7%29%2A%28x+-+%28-3%29%29+=+0
%28x+-+10%2F7%29%2A%28x+%2B+3%29+=+0
check:
Multiplying these, I get
x%5E2+-+%2810%2F7%29%2Ax+%2B+3x+-+30%2F7+=+0
Multiply both sides by 7
7x%5E2+-+10x+%2B+21x+-+30+=+0
7x%5E2+%2B+11x+-+30+=+0
OK