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Recent problems solved by 'ilana'

ilana answered: 307 problems
Jump to solutions: 0..29 , 30..59 , 60..89 , 90..119 , 120..149 , 150..179 , 180..209 , 210..239 , 240..269 , 270..299 , 300..329, >>Next

Miscellaneous_Word_Problems/633076: m varies directly as n and inversely as p. If m = 2 when n = 16 and p = 16, find p when m = 16 and n = 25
1 solutions

Answer 398654 by ilana(307) About Me  on 2012-07-30 04:09:41 (Show Source):
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If m varies directly as n, then m=k*n, where k is some number. If m also varies inversely as p, then m=k*n/p. So plug in the values to solve for k and get a general formula.
m=k*n/p (Note that (k*n)/p is the same as k*(n/p).)
2=k*16/16
2=k*1
2=k
So the formula is m=2*n/p. Now plug in the other values.
m=2*n/p
16=2*25/p
16=50/p
16*p=50 (I cross-multiplied.)
p=50/16
p=3.125


Volume/633075: a coal bin is 4 meters wide and 5 meters long. To what depth must it be filled to contain 60 cubic meters of coal?
My formula is s%5E2%2Ah
My solution is 4^2*5
=16*5
=80
I hope i got the answer right :)
1 solutions

Answer 398653 by ilana(307) About Me  on 2012-07-30 04:03:25 (Show Source):
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You are correct in using a volume formula and plugging in given values. The problem is you used the wrong volume formula and therefore had to plug in your values for the wrong variables. The formula you used, V=s^2*h, is for a rectangular prism with a square base. This coal bin has a rectangular base- it has 3 different dimensions instead of having 2 that are equal. So you need the formula Volume=length*width*height, or in this case, Volume=length*width*depth. Now let's plug in our values.
V=l*w*d
60=5*4*d
60=20*d
60/20=d
3=d
The bin must be filled to a depth of 3 meters.


Angles/474938: the difference between the measures of two supplementary angles is 20 degrees. Find the measure of each angle.
1 solutions

Answer 325686 by ilana(307) About Me  on 2011-07-27 06:49:53 (Show Source):
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If the measures are x and y degrees, and they are supplementary, then their sum is 180 degrees. So you can write and solve a system of equations.
x + y = 180
x - y = 20
Now you can use any method to solve. Let's use the elimination method by adding the equations together.
x + x + y - y = 180 + 20
2x = 200
x = 100
Now solve for y.
100 + y = 180
y = 80
So the angles measure 100 and 80 degrees.


test/466683: If rain is falling at the rate of 2 inches per hour, how many inches of rain will fall in x minutes? (A). 30/x. (B). x/30. (C). 60/x. (D). 2x
1 solutions

Answer 319970 by ilana(307) About Me  on 2011-07-02 23:51:21 (Show Source):
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You can just plug in 60 for x and see which answer gives you 2, since you know it should be 2 inches in 60 minutes.
The answer is B since 60/30 = 2.


Linear-systems/460260: i fogot the steps to eliminations.
0.3x - 0.2y = 4
0.5x + 0.3y = - 7/17
can someone help me
1 solutions

Answer 315727 by ilana(307) About Me  on 2011-06-12 18:09:44 (Show Source):
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To use the elimination method, make either the x terms or the y terms cancel out when you add or subtract the equations.
You can start by multiplying both equations by 10 to get rid of the decimals.
3x - 2y = 40
5x + 3y = -70/17
Multiply the first equation by 3 and the second equation by 2 so you can add -6y and 6y to get 0.
9x - 6y = 120
10x + 6y = -140/17
[I got -140/17 by multiplying -70/17 by 2. Anything you do to one side of the equation you have to do to the other in order for the equation to still work. So we multiplied each term on each side by 2.]
Now add the equations.
19x = 120 - 140/17
19x = (2040 - 140)/17
19x = 1900/17
x = 1900/(17*19)
x = 1900/323
Now plug this x into either equation to solve for y.
3x - 2y = 40
3(1900/323) - 2y = 40
5700/323 - 2y = 40
2y = 5700/323 - 40
2y = (5700 - 12920)/323
2y = -7220/323
y = -7220/646
The approximate solution is (5.88, -11.18).


Radicals/455637: determine the domain of sqrt 6-3x write answer in interval notation
1 solutions

Answer 312828 by ilana(307) About Me  on 2011-05-30 20:50:59 (Show Source):
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6-3x must be greater than or equal to 0.
-3x must be greater than or equal to -6.
x must be less than or equal to 2.
In interval notation: x is in (-infinity, 2]


test/455315: An isosceles triangle has a perimeter of 370 millimeters. The base of the triangle is 40 millimeters. Longer than the two equal sides. What is the lenght of each side?
Thank u : )
1 solutions

Answer 312625 by ilana(307) About Me  on 2011-05-29 19:45:56 (Show Source):
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Since the triangle is isosceles, the sides are the same length, x. The base is then x + 40.
So x + x + x + 40 = 370
3x + 40 = 370
3x = 330
x = 110
The lengths of the sides are 110 mm, 110 mm, and 150 mm.


Parallelograms/455343: The base of a parallelogram is 28.4 centimeters. The height is one fourth of the base. Find the area of the parallelogram
1 solutions

Answer 312624 by ilana(307) About Me  on 2011-05-29 19:43:33 (Show Source):
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The area of a parallelogram is base times height.
The height is one-fourth times the base, or 28.4/4 = 7.1 cm.
So the area is (28.4)(7.1) = 201.64 cm^2.


Mixture_Word_Problems/455325: Solve the system using the substitution method. If the system has no solution or an infinite number of solutions, state this.
5x+y=13
2x=-3y
1 solutions

Answer 312622 by ilana(307) About Me  on 2011-05-29 19:41:36 (Show Source):
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Substitution method means make one of the equations "x=_" or "y=_", and then substitute that into the other equation.
Since the first equation has a y with no coefficient, solve for y in that equation.
5x + y = 13 --> y = 13 - 5x
Now substitute "13 - 5x" for y in the second equation.
2x = -3y --> 2x = -3(13 - 5x)
Solve for x.
2x = -39 + 15x
39 = 15x - 2x
39 = 13x
x = 3
Now solve for y using the equation y = 13 - 5x
y = 13 - 5x
y = 13 - 5(3)
y = 13 - 15
y = -2
The solution is x=3, y=-2.


Geometry_Word_Problems/455327: The vectors (3,6) and (-2,k) are parallel. Find the value of k?
1 solutions

Answer 312612 by ilana(307) About Me  on 2011-05-29 19:21:13 (Show Source):
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If these vectors are parallel, the slope of the line through (0,0) and (3,6) must be equal to the slope of the line through (0,0) and (-2,k).
The slope of the line through (0,0) and (3,6) is (6-0)/(3-0), or 2.
So the slope through (0,0) and (-2,k) must be 2.
(k-0)/(-2-0)=2
k/-2=2
k=-4


Triangles/455332: Graph a rectangular solid that contains the point R (-1, 3, 2) and the origin as vertices. Label the points of each vertex.
1 solutions

Answer 312608 by ilana(307) About Me  on 2011-05-29 19:16:34 (Show Source):
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There are 8 vertices- 4 are part of the rectangle that is at height 0 like the origin. This is the bottom face of the rectangular solid. The other 4 are part of the rectangle that is at height 2 like the given point R. This is the top face of the rectangular solid.
The bottom rectangle has vertices (0, 0, 0), (0, 3, 0), (-1, 3, 0), and (-1, 0, 0). The top rectangle has vertices (-1, 3, 2), (-1, 0, 2), (0, 0, 2), and (0, 3, 2).


Radicals/453615: I need to simplify
sqrt(15)(2sqrt(3)-4sqrt(5))
1 solutions

Answer 311678 by ilana(307) About Me  on 2011-05-24 19:16:40 (Show Source):
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Distribute sqrt(15) to both terms.
sqrt(15)(2sqrt(3) - 4sqrt(5))
= 2sqrt(15)sqrt(3) - 4sqrt(15)sqrt(5)
= 2sqrt(5)sqrt(3)sqrt(3) - 4sqrt(5)sqrt(3)sqrt(5)
= 2sqrt(5)*3 - 4sqrt(3)*5
= 6sqrt(5) - 20sqrt(3)


Probability-and-statistics/453680: A bag contains yellow and red blocks, there are 4 more red blocks than yellow. When pulling two blocks out, one at a time, you can not replace the first block. What is an expression that represents the probability of pulling out a red block first, then a yellow block?
Thank you.
1 solutions

Answer 311677 by ilana(307) About Me  on 2011-05-24 19:10:27 (Show Source):
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Use x for the number of yellow blocks. Then there are x + 4 red blocks. So there are x + x + 4, or 2x + 4 blocks in all.
P(red) = (x + 4)/(2x + 4)
P(yellow after red) = x/(2x + 3)
So the probability is the product, x(x + 4)/(2x + 4)(2x + 3).


Geometry_Word_Problems/453667: a square has an area of 36 square centemeters a rectangle has the same area as the square if the rectangle long sides mesure 9 centemters what is the rectangles perimeter

1 solutions

Answer 311676 by ilana(307) About Me  on 2011-05-24 19:04:15 (Show Source):
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If the rectangle's area is 36 square centimeters, and its length is 9 cm, then its width must be 36/9 = 4 cm.
perimeter = 2l + 2w
= 2*9 + 2*4
= 18 + 8
= 26 cm


Word_Problems_With_Coins/453640: In a coin collection there are 9 pennies, 8 nickels, 12 dimes, 16 quarters, 11 half-dollars and 4 dollar pieces. A coin is randomly selected from the collection by a blind folded boy who gets to keep the coin picked. What is the expected value?
1 solutions

Answer 311674 by ilana(307) About Me  on 2011-05-24 18:52:53 (Show Source):
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The expected value is the sum of each probability times its value.
P(penny) = 9/60
P(nickel) = 8/60
P(dime) = 12/60
P(quarter) = 16/60
P(half-dollar) = 11/60
P(dollar) = 4/60
Expected value = 1*9/60 + 5*8/60 + 10*12/60 + 25*16/60 + 50*11/60 + 100*4/60
= (9 + 40 + 120 + 400 + 550 + 400)/60
= 1519/60
= approx. $25.32


Geometry_Word_Problems/453659: Given U = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}, A = {12, 14, 16, 18, 20}, and B = {11, 13, 14, 15, 18, 19, 20}.
Find A′ ∩ B′. Show your work, finding A’, then B’ then find their intersection.
1 solutions

Answer 311673 by ilana(307) About Me  on 2011-05-24 18:43:54 (Show Source):
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A' contains the elements that are in U but not A.
A' = {10, 11, 13, 15, 17, 19}
B' contains the elements that are in U but not B.
B' = {10, 12, 16, 17}
Their intersection contains the elements in both.
A′ ∩ B′ = {10, 17}


Radicals/452762: what is the midpoint of the line segment from -3,4 and -1,-6 ?
1 solutions

Answer 311164 by ilana(307) About Me  on 2011-05-22 18:49:55 (Show Source):
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Find the average of the x values and the average of the y values.
x: (-3 + -1)/2 = -4/2 = -2
y: (4 + -6)/2 = -2/2 = -1
The midpoint is (-2, -1).


Graphs/452728: As a mother, I am having problems remembering the - and + on the algebra.
9<-3X
If I am correct then it would be -31 solutions

Answer 311162 by ilana(307) About Me  on 2011-05-22 18:46:43 (Show Source):
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No, it would be -3 > x. When you divide by a negative number (-3 here), you need to flip the sign. You can also test the direction of the inequality symbol by testing a value for x. In the original inequality, 9<-3x, the value -10 works for x. (9<30 is true.) But if the solution were -3

Evaluation_Word_Problems/452748: what value of x will make the rational expression x-3/x+7 undefined?
1 solutions

Answer 311158 by ilana(307) About Me  on 2011-05-22 18:41:29 (Show Source):
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A rational expression is undefined when the denominator is 0. So in this case, solve the equation x + 7 = 0. It will be undefined when x = -7.


Probability-and-statistics/452753: A bag contains 25 gummy bears: five each of green, red, black, orange, and yellow. If you pick 2 gummy bears from the bag, what is the probability that the gummy bears will be the same color?

1 solutions

Answer 311157 by ilana(307) About Me  on 2011-05-22 18:39:40 (Show Source):
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The first gummy bear you pick can be any color, so it can be any one of the 25. The probability of that is 25/25, or 1. The second then has to be one of the 4 others of that color. The probability of that is 4/24, or 1/6. So the probability is 1 * 1/6, or 1/6.


Travel_Word_Problems/452758: What is the 5017th number in the sequence?
3, 2, 8, 9, 3, 2, 8, 9, ..., _____
Thanks for helping
1 solutions

Answer 311155 by ilana(307) About Me  on 2011-05-22 18:35:30 (Show Source):
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There are 4 terms that keep repeating. So any number divisible by 4 (4, 8, 12, 16, 20,...) will be 9. Which number near 5017 will that be? #5016. That means the 5017th number is the one right after, which will be 3.


Rational-functions/452756: Please help me solve this problem?
^3sqrt5x+8 +6=1 what is x?
1 solutions

Answer 311154 by ilana(307) About Me  on 2011-05-22 18:32:35 (Show Source):
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^3sqrt5x+8 +6=1
Subtract 6 from each side.
^3sqrt5x+8 = 1 - 6
^3sqrt5x+8 = -5
Cube each side.
5x + 8 = (-5)^3
5x + 8 = -125
Subtract 8 from each side.
5x = -133
x = -133/5, or -26.6


Linear_Equations_And_Systems_Word_Problems/452750: Susan wants to mix 10 pounds of Virginia peanuts that cost $3.50 a pound with Spanish peanuts that cost $3.00 a pound to obtain a mixture that costs $3.40 a pound. How many pounds of Spanish peanuts should she use?
I have given this problem some thought but I do not know how you would solve.
Thanks

1 solutions

Answer 311153 by ilana(307) About Me  on 2011-05-22 18:29:05 (Show Source):
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There will be 10 pounds of Virginia peanuts and x pounds of Spanish peanuts. The total cost will be 3.5(10) + 3(x). The total amount of pounds will be 10 + x. You want the cost per pound to be $3.40, so the (total cost)/(total pounds) should be 3.4, so solve the equation:
(35 + 3x)/(10 + x) = 3.4
35 + 3x = 3.4(10 + x)
35 + 3x = 34 + 3.4x
1 = 0.4x
x = 1/(4/10)
x = 10/4
x = 2.5
She should use 2.5 pounds of Spanish peanuts.
Then the total cost will be 35 + 7.5, or $42.50.
The total weight will be 10 + 2.5, or 12.5 pounds.
The total cost per pound will be 42.5/12.5 = $3.40/pound.


Rectangles/452744: An airplane ticket has an area of 70 square centimeters. Its perimeter is 34 centimeters. What are the dimensions of the ticket?
1 solutions

Answer 311152 by ilana(307) About Me  on 2011-05-22 18:22:19 (Show Source):
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If it's length and width are x and y, then its area is xy and its perimeter is 2x + 2y. So you can write 2 equations and solve the system.
xy = 70
2x + 2y = 34
Substitute 70/y for x (from the first equation) into the second equation.
2(70/y) + 2y = 34
140/y + 2y = 34
Multiply everything by y.
140 + 2y^2 = 34y
2y^2 - 34y + 140 = 0
Divide everything by 2.
y^2 - 17y + 70 = 0
(y - 10)(y - 7) = 0
y = 7 or 10
So the dimensions are 7 cm by 10 cm.


Miscellaneous_Word_Problems/452737: A lot is in the shape of a right triangle. The shorter leg measures 180 m. The hypotenuse is 60 m
longer than the length of the longer leg. How long is the longer leg?
1 solutions

Answer 311149 by ilana(307) About Me  on 2011-05-22 17:48:19 (Show Source):
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Say the length of the longer leg is x. Then the hypotenuse measures x + 60. So, using the Pythagorean Theorem, x^2 + 180^2 = (x + 60)^2.
x^2 + 32400 = x^2 + 120x + 3600
32400 = 120x + 3600
120x = 28800
x = 240
The longer leg measures 240 m.


Volume/452715: What is the equation of the parabola that moves the parent graph y=x^2 to the left 9 units?
1 solutions

Answer 311147 by ilana(307) About Me  on 2011-05-22 17:27:56 (Show Source):
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Shifting the parabola to the left 9 units means that to get a certain y-value, you now need to add 9 to the x-value to compensate for the shift. So you plug in "x + 9" for x. So the equation is y=(x+9)^2.


Quadratic_Equations/452709: Hello,
I'm just a little confused by what the following question is asking:
What two numbers are represented by each of the following?
1. -6 plus or minus (sqrt 6) I think it is asking for the answer of -6 + (sqrt 6) and -6 - (sqrt 6) since nothing can be factored out of (sqrt 6).
2. 4/3 plus or minus (i sqrt 2) /3 I think the answers would be (4+ (isqrt2))/3 and ((4 - (i sqrt 2))/3
but it could be 1 + ((1+isqrt2))/3 and 1 - ((1+isqrt2))/3
and the next question:
what must be added to make the given expression a trinomial square?
m^2 - 4m + ? I think the answer is 4, if the equation were factored it would be (m-2)(m-2)
a^2 + 12a + ? not sure how to do this equation however.

please show me how to correctly do these equations. Thank you
1 solutions

Answer 311146 by ilana(307) About Me  on 2011-05-22 17:21:13 (Show Source):
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1. I think you are correct.
2. I think your first choice is correct.
These seem to just want you to know the meaning of "plus or minus".
3. You are correct, 4 is the answer.
4. Look at what you did for #3. You took the coefficient of m and divided it by 2, and then squared it. (-4/2 = -2, and (-2)^2 = 4.) This comes from the fact that (a + b)^2 = a^2 + 2ab + b^2. So in this case, for #4, divide 12 by 2 (and get 6), and then square that (and get 36). So the answer is 36. The factored expression would be (a + 6)(a + 6).


Rectangles/452698: A rectangular parking lot has a length that is 3 yards greater than the width. The area of the parking lot is 700 square yards. What is the length and the width?
1 solutions

Answer 311142 by ilana(307) About Me  on 2011-05-22 17:13:09 (Show Source):
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Write an equation to represent the situation. Call the width x. Then the length is x + 3. So the area is length times width, or x*(x + 3).
x(x + 3) = 700
x^2 + 3x = 700
x^2 + 3x - 700 = 0
Use the Quadratic formula:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-3+%2B-+sqrt%28+3%5E2-4%2A1%2A-700%29+%29%29%2F%282%2A1%29+
x+=+%28-3+%2B-+sqrt%28+9%2B2800+%29%29%2F%282%29+
x+=+%28-3+%2B-+sqrt%28+2809+%29%29%2F%282%29+
x = 25
So the length is x + 3, or 28. The rectangle is 25 yards wide by 28 yards long. (You also could have factored x^2 + 3x - 700 into (x - 25)(x + 28) to get this answer.


Probability-and-statistics/452701: you spin the pointer on the spinner. Find the probability that the spinner will stop on a number greater than 1
1 solutions

Answer 311138 by ilana(307) About Me  on 2011-05-22 16:57:00 (Show Source):
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Depends what the spinner looks like. Assuming is has 6 sections, all the same size, with numbers 1, 2, 3, 4, 5, and 6, the probability of getting a number greater than 1 is 5/6, since 5 numbers (2, 3, 4, 5, and 6) of the 6 possibilities will qualify.


Graphs/450958: find the equation for the line having a slope = 3/4 & a x-intercept of -2. put answer in the form y=mx+b.
1 solutions

Answer 310117 by ilana(307) About Me  on 2011-05-17 21:40:31 (Show Source):
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For the line represented by the equation y = mx + b, m is the slope and b is the y-intercept. So plug in 3/4 for m and -2 for b. The equation is y = 3/4 * x + (-2), or y = 3/4 * x - 2.


Quadratic_Equations/450956: Why Can The Variable X Be Substituded For Two Numbers?
1 solutions

Answer 310108 by ilana(307) About Me  on 2011-05-17 21:26:45 (Show Source):
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It looks like you are trying to figure out why 2 numbers can both be substituted in for x in a quadratic equation. The reason is a quadratic equation has 2 values of x that make it true. An equation can have even more than 2 solutions- the equation x + 3 = x + 5 - 2 is true for any value of x.
You can think of it graphically, too. The graph of a linear equation is a line. When you solve the equation x + 5 = 10, you get the solution x = 5. That means that when you graph the equation y = x + 5, the value of y is 10 when x = 5.
The graph of a quadratic equation is a parabola- it looks like a U. So sometimes more than one x-value will give the same y-value. x^2 - 2 = 14 when x is 4 and -4. When you look at the graph of y = x^2 - 2, the value of y is 14 when x is 4 and -4.