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nerdybill answered: 6946 problems
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Equations/454804: Andrew can paint a room by himself in 8 hours. With the help of Mike, it will only take him 3 hours. How long does it take Mike by him self?
1 solutions
Answer 312249 by nerdybill(6948) on 2011-05-27 16:44:21 (Show Source):
You can put this solution on YOUR website!Andrew can paint a room by himself in 8 hours. With the help of Mike, it will only take him 3 hours. How long does it take Mike by him self?
.
Let x = time (hours) it takes for Mike by himself
then
3(1/8 + 1/x) = 1
multiplying both sides by 8x:
3(x + 8) = 8x
3x + 24 = 8x
24 = 5x
24/5 = x
4.8 hours = x
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test/454568: Find the area of an isosceles triangle with legs of 12cm and a base of 6cm. 1 solutions
Answer 312118 by nerdybill(6948) on 2011-05-26 19:56:04 (Show Source):
You can put this solution on YOUR website!Find the area of an isosceles triangle with legs of 12cm and a base of 6cm.
.
area of any triangle = (1/2)bh
where
b is base
h is height
.
the problem gives you the base (b) as 6 cm.
You need to find the height (h). The height (h) splits the isosceles triangle in half and it is a right triangle -- use Pythagorean theorem to find h:
3^2 + h^2 = 12^2
9 + h^2 = 144
h^2 = 135
h = sqrt(135)
h = sqrt(5*3*3*3)
h = 9*sqrt(15)
.
area = (1/2)bh
area = (1/2)(6)(9*sqrt(15))
area = (3)(9*sqrt(15))
area = 27*sqrt(15) sq cm
area = 104.57 sq cm
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logarithm/454385: Solve the equation & check your answer(s):
ln(2-2x)=ln(x+5)+ln(x+4) 1 solutions
Answer 311981 by nerdybill(6948) on 2011-05-26 11:20:38 (Show Source):
You can put this solution on YOUR website!ln(2-2x)=ln(x+5)+ln(x+4)
ln(2-2x)=ln(x+5)(x+4)
(2-2x)=(x+5)(x+4)
2-2x= x^2 +9x + 20
2 = x^2 + 11x + 20
0 = x^2 + 11x + 18
0 = (x+9)(x+2)
x = {-9,-2}
Testing each of the solution above, we see that -9 is an "extraneous solution" and must be thrown out leaving:
x = -2
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Rate-of-work-word-problems/453460: if it take 4 hours to fill a pool with the drain closed and 5 hours to empty a pool with the drain open, how long does it take to fill a pool with the drain open 1 solutions
Answer 311552 by nerdybill(6948) on 2011-05-24 11:24:06 (Show Source):
You can put this solution on YOUR website!if it take 4 hours to fill a pool with the drain closed and 5 hours to empty a pool with the drain open, how long does it take to fill a pool with the drain open.
.
Let x = time (hours) it takes to fill pool w/drain open
then
x(1/4 - 1/5) = 1
multiplying both sides by 20:
x(5 - 4) = 20
x(1) = 20
x = 20 hours
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Surface-area/453467: the total area of a sphere is 144 pie square centimeters. what is the diameter? 1 solutions
Answer 311551 by nerdybill(6948) on 2011-05-24 11:20:11 (Show Source):
You can put this solution on YOUR website!the total area of a sphere is 144 pie square centimeters. what is the diameter?
.
since the area of a sphere is given as:
4(pi)r^2
.
We set the above equal to 144 to find the radius:
4(pi)r^2 = 144(pi)
dividing both sides by pi:
4r^2 = 144
dividing both sides by 4:
r^2 = 36
take the square root of both sides:
r = 6 cm
.
But, the problem wanted the diameter...
diameter = 2r
diameter = 2(6)
diameter = 12 cm (answer)
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Pythagorean-theorem/453437: A 15 m pole is leaning against a wall. The foot of the pole is 10 m from the wall. What is the angle that the pole makes with the ground? 1 solutions
Answer 311548 by nerdybill(6948) on 2011-05-24 10:01:15 (Show Source):
You can put this solution on YOUR website!A 15 m pole is leaning against a wall. The foot of the pole is 10 m from the wall. What is the angle that the pole makes with the ground?
.
Apply Trigonometry...
Let x = angle
then
cos x = 10/15
x = cos^(-1)(10/15)
x = cos^(-1)(2/3)
x = 48.2 degrees
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Triangles/453127: If a right triangle has legs of 6 cm and 8 cm, then the hypotenuse is ? 1 solutions
Answer 311344 by nerdybill(6948) on 2011-05-23 14:08:13 (Show Source):
You can put this solution on YOUR website!If a right triangle has legs of 6 cm and 8 cm, then the hypotenuse is ?
Apply Pythagorean theorem:
Let h = hypotenuse
then
6^2 + 8^2 = h^2
36 + 64 = h^2
100 = h^2
10 cm = h
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logarithm/453069: Determine the positive root of the following equation:
log3(c - 4) + log3(c + 6) = 4.
(Please round your answer to one decimal place.)
Answer
1 solutions
Answer 311307 by nerdybill(6948) on 2011-05-23 12:05:47 (Show Source):
You can put this solution on YOUR website!log3(c - 4) + log3(c + 6) = 4
log3(c - 4)(c + 6) = 4
(c - 4)(c + 6) = 3^4
c^2 + 6c - 4c -24 = 81
c^2 + 2c -105 = 0
apply the quadratic formula to find the roots:
c = {9.3, -11.3}
throw out the negative root leaving:
c = 9.3
.
details of quadratic to follow:
| Solved by pluggable solver: SOLVE quadratic equation with variable |
Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.
First, we need to compute the discriminant : .
Discriminant d=424 is greater than zero. That means that there are two solutions: .


Quadratic expression can be factored:

Again, the answer is: 9.295630140987, -11.295630140987.
Here's your graph:
 |
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Equations/453073: find vertex of porabola y = 6 x + 7 - x^2 1 solutions
Answer 311306 by nerdybill(6948) on 2011-05-23 11:59:36 (Show Source):
You can put this solution on YOUR website!y = 6 x + 7 - x^2
rearranging:
y = -x^2 + 6x + 7
.
The x-coordinate of the vertex is at:
x = -b/(2a) = -6/(2*(-1)) = -6/(-2) = 3
.
The y-coordinate:
y = -x^2 + 6x + 7
y = -3^2 + 6(3) + 7
y = -9 + 18 + 7
y = 16
.
Answer: (3, 16)
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logarithm/453080: Find the approximate solution to the equation.
5x + 3 = 2x - 6
(If necessary, please round your answer to 4 decimal
1 solutions
Answer 311305 by nerdybill(6948) on 2011-05-23 11:53:25 (Show Source):
You can put this solution on YOUR website!Next time, you should write your expression as:
5^(x+3) = 2(x-6)
log(5) * (x+3) = log(2) * (x-6)
xlog(5) + 3log(5) = xlog(2) - 6log(2)
xlog(5) - xlog(2) = -6log(2) - 3log(5)
x(log(5) - log(2)) = -6log(2) - 3log(5)
x = (-6log(2) - 3log(5)) / (log(5) - log(2))
x = (-3.9) / (.40)
x = -9.76
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Problems-with-consecutive-odd-even-integers/452484: Find two consecutive negative integers whose product is 90
-thanks 1 solutions
Answer 311047 by nerdybill(6948) on 2011-05-22 08:19:21 (Show Source):
You can put this solution on YOUR website!Find two consecutive negative integers whose product is 90
.
Let x = first negative answer
then
x+1 = second negative answer
x(x+1) = 90
x^2 + x = 90
x^2 + x - 90 = 0
(x+10)(x-9) = 0
x = (-10, 9)
Since we're looking for a negative answer, throw out the positive answer leaving:
x = -10 (first negative number)
.
Second negative number"
x+1 = -10+1 = -9
.
Answer: -10 and -9
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Miscellaneous_Word_Problems/452493: an element decays in such a way that every 50 years the amount of the element of the element has decreased by 15% in the year 1900,120mg of element was present.
a)what is amount in 2000
1 solutions
Answer 311046 by nerdybill(6948) on 2011-05-22 08:15:02 (Show Source):
You can put this solution on YOUR website!an element decays in such a way that every 50 years the amount of the element of the element has decreased by 15% in the year 1900,120mg of element was present.
a)what is amount in 2000
.
A = Pe^(rt)
where
A is amount after time t
P is the initial amount
r is the rate of growth/decline
t is time
.
first, we determine r...
Let x = initial amount
then
from: "an element decays in such a way that every 50 years the amount of the element of the element has decreased by 15%"
x - .15x = xe^(50r)
x(1 - .15) = xe^(50r)
(1 - .15) = e^(50r)
.85 = e^(50r)
ln(.85) = 50r
ln(.85)/50 = r
-0.0033 = r
.
Our formula then is:
A = Pe^(-0.0033t)
.
Now, we can answer the question:
in the year 1900,120mg of element was present.
a)what is amount in 2000
t = 2000-1900 = 100
A = 120e^(-0.0033*100)
A = 120e^(-0.33)
A = 86.7 mg
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Expressions-with-variables/452500: Algebraic expression:
1.Eight less than e
2.Five subtracted from t
3.The sum of x and y
4.one more than a number p
5.The product of v and 4 times i 1 solutions
Answer 311045 by nerdybill(6948) on 2011-05-22 08:01:14 (Show Source):
You can put this solution on YOUR website!Algebraic expression:
1.Eight less than e
8 - e
2.Five subtracted from t
t - 5
3.The sum of x and y
x + y
4.one more than a number p
p + 1
5.The product of v and 4 times i
v(4i)
or
4iv
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Circles/452433: A circle has a radius of 5 cm ..what is the length of an arc measuring 80 degrees 1 solutions
Answer 311044 by nerdybill(6948) on 2011-05-22 07:59:31 (Show Source):
You can put this solution on YOUR website! A circle has a radius of 5 cm ..what is the length of an arc measuring 80 degrees
.
circumference of a circle = d(pi)
circumference of a circle = 2r(pi)
circumference of a circle = 2(5)(3.14)
circumference of a circle = 31.4 cm
.
Since there is 360 deg in a circle:
length of the arc must be:
80/360 * 31.4 = 6.98 cm
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Triangles/452472: a right triangle has a leg that measures 5 meters, the angle at the intersection of that same leg and the hypoteneuese is 35 degrees.... How do you find the measure of the hypoteneuese? 1 solutions
Answer 311029 by nerdybill(6948) on 2011-05-22 00:22:47 (Show Source):
You can put this solution on YOUR website!a right triangle has a leg that measures 5 meters, the angle at the intersection of that same leg and the hypoteneuese is 35 degrees.... How do you find the measure of the hypoteneuese?
.
You apply trigonometry.
cos = adjacent/hypotenuse
.
Let h = hypotenuse
then
cos 35 = 5/h
h*cos 35 = 5
h = 5/cos 35
h = 6.10 meters
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Linear_Equations_And_Systems_Word_Problems/452262: I hope this is a linear equation and that someone can help me convert it from words to and equation and graph.
I need to illustrate the decline in the herring population over the years and estimate what will happen if the trend continues. I've spent all day researching the information and now I have no idea how to put it together, or even if it belongs together :0
Every year the herring returning to the Stonybrook Run to spawn is declining as overfishing, water pollution, and loss of habit takes a toll on their numbers.
In 2000, you could count 100 herring go through the run in 1 minute, but by 2005, it took 5 minutes to count the same number.
The count in 2010 took 10 minutes to count the 100 fish. If the trend continues how long will it take count 100 herring in 2015? 1 solutions
Answer 310934 by nerdybill(6948) on 2011-05-21 09:19:07 (Show Source):
You can put this solution on YOUR website!Create a table of data:
year time
2000 1
2005 5
2010 10
.
Plot the above three points on graph paper.
Because the dots appears to be in a straight line, you can assume it is linear.
.
Determine slope:
m = (y2-y1)/(x2-x1) using first and last points
m = (10-1)/(2010-2000)
m = (9)/(10)
m = 9/10
.
using the slope above and one point (2000,1)
plug it into the "point-slope" form:
y - y1 = m(x - x1)
y - 1 = (9/10)(x - 2000)
y - 1 = (9/10)x - (9/10)2000
y - 1 = (9/10)x - (9)200
y - 1 = (9/10)x - 1800
y = (9/10)x - 1801 (this is your equation)
.
For, 2015:
y = (9/10)x - 1801
y = (9/10)2015 - 1801
y = (9)201.5 - 1801
y = (9)201.5 - 1801
y = 1813.5 - 1801
y = 12.5 minutes
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Proportions/452179: One number is 4 more than 3/8 of another number. Total of both is 427. Please give formula. Thanks 1 solutions
Answer 310831 by nerdybill(6948) on 2011-05-20 18:19:10 (Show Source):
You can put this solution on YOUR website!One number is 4 more than 3/8 of another number. Total of both is 427.
.
Let x = one number
and y = another number
.
From: "One number is 4 more than 3/8 of another number."
x = 4+ (3/8)y (equation 1)
.
From: "Total of both is 427"
x + y = 427 (equation 2)
.
Solve equation 2 for y:
x + y = 427
y = 427-x
.
Substitute above into equation 1 to find x:
x = 4+ (3/8)y
x = 4+ (3/8)(427-x)
8x = 32+ (3)(427-x)
8x = 32+ 1281-3x
11x = 32+ 1281
11x = 1313
x = 119.36
.
Substitute above into equation 2 to find y:
x + y = 427
119.36 + y = 427
y = 307.64
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Quadratic_Equations/451697: Find equation of line passing through the point (5,-2) and (-3,4)
I got the answer y=(-3/4)x+7/4 but I don't know how
Please show me step by step to get the answer. thanks 1 solutions
Answer 310597 by nerdybill(6948) on 2011-05-19 14:16:40 (Show Source):
You can put this solution on YOUR website!Find equation of line passing through the point (5,-2) and (-3,4)
.
First, find the slope:
m = (y2-y1)/(x2-x1)
m = (4-(-2))/(-3-5)
m = (4+2)/(-3-5)
m = (6)/(-8)
m = -3/4
.
Next, use one of the two given points (5, -2) and the slope above -- plug it into the "point-slope" form:
y - y1 = m(x - x1)
y - (-2) = (-3/4)(x - 5)
y + 2 = (-3/4)x + 15/4
y = (-3/4)x + 15/4 - 2
y = (-3/4)x + 15/4 - 8/4
y = (-3/4)x + 7/4
.
So, YES, you are correct!
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Rate-of-work-word-problems/451656: A stone is thrown directly upward from a height of 30ft with a velocity of 60ft/sec. The height of the stone t seconds after it has been thrown is given by the function s(t)= - 16t^2 + 16t + 30. Find the time at which the stone reaches its maximum height and find that maximum height. 1 solutions
Answer 310559 by nerdybill(6948) on 2011-05-19 11:49:39 (Show Source):
You can put this solution on YOUR website!A stone is thrown directly upward from a height of 30ft with a velocity of 60ft/sec. The height of the stone t seconds after it has been thrown is given by the function s(t)= - 16t^2 + 16t + 30. Find the time at which the stone reaches its maximum height and find that maximum height.
.
Time reaching maximum height is at the vertex:
t = -b/(2a)
t = -16/(2*(-16))
t = -16/(-32)
t = 1/2 seconds
.
Maximum height:
s(1/2)= - 16(1/2)^2 + 16(1/2) + 30
s(1/2)= - 16(1/4) + 8 + 30
s(1/2)= - 4 + 8 + 30
s(1/2)= 34 feet
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Numbers_Word_Problems/451650: the difference between the tens digit and the unit digit of a two digit number is 3. Suppose the tens digit is one less than twice the units digit. what is the number? 1 solutions
Answer 310557 by nerdybill(6948) on 2011-05-19 11:36:03 (Show Source):
You can put this solution on YOUR website!the difference between the tens digit and the unit digit of a two digit number is 3. Suppose the tens digit is one less than twice the units digit. what is the number?
.
Let x = tens digit
and y = units digit
then
from: "the difference between the tens digit and the unit digit of a two digit number is 3"
x-y = 3 (equation 1)
from: "Suppose the tens digit is one less than twice the units digit"
x = 2y-1 (equation 2)
.
Start with equation 1:
x-y = 3
substitute definition of x from equation 2:
2y-1-y = 3
y-1 = 3
y = 4
.
Substitute above into equation 1 to find x:
x-y = 3
x-4 = 3
x = 7
.
Solution: the number is 74
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Angles/451643: Two angles are complementary. they have measures of (7x+2)degree and (3x-2)degree, respectively. what is the value of x?
1 solutions
Answer 310549 by nerdybill(6948) on 2011-05-19 11:09:28 (Show Source):
You can put this solution on YOUR website!Two angles are complementary. they have measures of (7x+2)degree and (3x-2)degree, respectively. what is the value of x?
.
Since the sum of complementary angles is 90 degrees we get:
(7x+2) + (3x-2) = 90
7x+2 + 3x-2 = 90
10x+2-2 = 90
10x = 90
x = 9
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