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unlockmath answered: 1598 problems
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Volume/299090: Find the surface area, to the nearest tenth, of a cylinder with diameter 5cm and height 8cm. (S=2 pi rh+2 pi r2).
1 solutions

Answer 215029 by unlockmath(1599) About Me  on 2010-05-01 15:53:55 (Show Source):
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Hello,
Since we know the formula is S=2 pi rh+2 pi r2 all we need to do is plug in the values we know to get:
S=2 pi 2.5(8)+ 2 pi 2.5^2 Do the calculation and we get:
S=40 pi + 12.5 pi Combine to get:
S=52.5 pi square cm We could plug in 3.14 for pi to get:
164.9 sq cm (rounded to the nearest tenth)
Make Sense?
RJ Check out a book I wrote on the basics of math:
www.math-unlock.com


Polynomials-and-rational-expressions/299087: If the area of a square is represented by x%5E2-4x%2B4, what is the perimeter?
thank you.
1 solutions

Answer 215027 by unlockmath(1599) About Me  on 2010-05-01 15:40:59 (Show Source):
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Hello,
First let's factor this out (x^2-4x+4) to get:
(x-2)(x-2)=0 Now we know the sides are x-2 so we do this to find the perimeter:
(x-2)+ (x-2) + (x-2) + (x-2)
This will give us:
4x-8 as the perimeter.
RJ www.math-unlock.com


Quadratic_Equations/298131: HELP!!!!!!!!
I don't get this problem at ALL!!!
If it takes a ball 8 seconds to hit the ground, from what height did it fall?
1 solutions

Answer 214557 by unlockmath(1599) About Me  on 2010-04-28 23:19:17 (Show Source):
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Hello,
The equation we need to use is:
Distance=7t^2 Plug in 8 for t and we get:
Distance=7(64) Multiplied out to get:
D = 448 feet
RJ
www.math-unlock.com


Polynomials-and-rational-expressions/297827: Subtract. Simplify if possible.
W^2/11w^2-11w - 1/11w-11
1 solutions

Answer 214469 by unlockmath(1599) About Me  on 2010-04-28 16:56:05 (Show Source):
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Hello,
In the following W^2/11w^2-11w - 1/11w-11 we can combine like terms to look like:
W^2/11w^2-122/11(w)-11 The w^2 will cancel out to be:
1/11-122/11(w)-11 Then combine like terms to get:
-122/11(w)-120/11
Make sense?
RJ
www:math-unlock.com


logarithm/297833: Please help.
Evaluate each of the following
1. Log81^9 ( the log base is 81 and the exponent is 9)
Can you tell me how I can type the base and exponent into the system?




1 solutions

Answer 214465 by unlockmath(1599) About Me  on 2010-04-28 16:45:21 (Show Source):
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Hello,
Understanding the log is sometimes tough for students. This (Log81^9) is read as:
81 to what exponent will give you 9?
The exponent will be 1/2 and be like this:
81^(1/2)=9 Or you can write it like this:
Square root of 81 = 9
Make sense?
RJ
Check out a book I wrote on the basics of math:
www.math-unlock.com


Age_Word_Problems/297898: Roberta now is 3 times as old as Ricky. Five years from now she will be twice as old as Ricky is then. What are the ages of both Ricky and Roberta?
1 solutions

Answer 214458 by unlockmath(1599) About Me  on 2010-04-28 16:35:47 (Show Source):
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Hello,
We can set up 2 equation like this: (Let x be Ricky and y be Roberta)
y=3x
y+5=2(x+5) Solve by substitution:
3x+5=2x+10 Subtract 2x and 5 from both sides to get:
x=5
There we go Ricky is now 5 years old. I'll let you figure out the age of Roberta.
Make sense?
RJ
There is a book I wrote on the basics that would help:
www.math-unlock.com


Polynomials-and-rational-expressions/296704: Reduce the rational expression to lowest terms.
2x + 6 / 2x squared + 14x + 24
1 solutions

Answer 213767 by unlockmath(1599) About Me  on 2010-04-26 12:47:26 (Show Source):
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Hello,
Let's first rewrite this 2x + 6 / 2x squared + 14x + 24 as:
2x + 6 / 2x^2 + 14x + 24 Both top and bottom and be factored as:
2(x+3)/2(x+3)(x+4) The (x+3) and 2 cancel out to leave us:
1/(x+4)
Make Sense?
RJ
Check out a book I wrote:
www.math-unlock.com


Numbers_Word_Problems/296639: find three consecutive even integers so that the largest is 2 times more than
the smallest?

1 solutions

Answer 213764 by unlockmath(1599) About Me  on 2010-04-26 12:39:59 (Show Source):
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Hello,
Let "x" represent an even integer. "x+4" will show the largest. Now we can set up an equation to be:
2x=(x+4) Subtract x from both sides to get:
x=4
So the integers are 4,6,8
There we go. Make sense?
There's a book I wrote covering the basics:
www.math-unlock.com


Finance/296116: Ok, I am totally confused on how to solve this one with the exponets being so high and square roots. thxs lauren
sqrt (64x^5) / sqrt (121x^7)
1 solutions

Answer 213474 by unlockmath(1599) About Me  on 2010-04-25 01:04:23 (Show Source):
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Hello,
First off we can rewrite this as:
(sqrt 64 sqrt x^5) / (sqrt 121 sqrt x^7) Then we can get:
8 sqrt x^5/ 11 sqrt x^7 We can now rewrite this as:
8(x^5/2)/11 (x^7/2) Now bring this denominator up with the numerator:
8 (x^5/2)(x^-7/2)/11 This will result in:
8 (x^-2/2)/11 Now we can rewrite it as:
8/11x
Make sense?
RJ
www.math-unlock.com


Exponents-negative-and-fractional/296020: Simplify. Write your answer with positive exponents only. a^-3(a^3b^4)^-5 divided by b^-3
Thanks in advance.
1 solutions

Answer 213361 by unlockmath(1599) About Me  on 2010-04-24 14:10:26 (Show Source):
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Hello,
Moving a negative exponent from numerator to denominator or the other way removes the negative to positive. So in this a^-3(a^3b^4)^-5 divided by b^-3 we get:
b^3/a^3(a^3b^4)^5
There we go, all positive.
Make sense?
RJ
www.math-unlock.com


Proportions/296013: A printing press produces 4,200 posters per hour. at this rate,in how many minutes can the printing press produces 840 posters
(A) 0.2 (B) 1.5 (C) 5 (D) 12 (E) 70

1 solutions

Answer 213360 by unlockmath(1599) About Me  on 2010-04-24 14:04:40 (Show Source):
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Hello,
WE can set up a proportion as follows:
4200/60=840/x (Hint: convert hour to minutes)
Cross multiply to get:
4200x=50400 Divide both sides by 4200 to get:
x=12 minutes
Make sense?
There's a book I wrote that explains the basics at:
www.math-unlock.com


Equations/295092: -5/8-6/-5

1 solutions

Answer 212717 by unlockmath(1599) About Me  on 2010-04-21 21:48:39 (Show Source):
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Hello,
The key to adding or subtracting fractions is having the same denominator.
This -5/8-6/-5 we'll set up the denominator to be 40 so it will look like this:
-25/40+48/40 will give us: (hint: 2 negatives gives us a positive)
23/40
Make sense?
RJ
Get a book I wrote on the basics of math at:
www.math-unlock.com


expressions/294824: 25(x-4)+3x=77-2(x-3)
1 solutions

Answer 212572 by unlockmath(1599) About Me  on 2010-04-21 13:58:56 (Show Source):
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Hello,
This 25(x-4)+3x=77-2(x-3) can be expanded out to:
25x-100+3x=77-2x+6 Now combine like terms and add 100 to both sides to get:
28x=-2x+183 Add 2x from both sides and divide by 30 to get:
x=183/30 or 6.1
Check the answer in the original to see if it comes out OK.
RJ
www.math-unlock.com


Rectangles/294820: The length of a room is 8 feet longer than twice the width. The perimeter is 70 feet. Find the length and the width of the room.

1 solutions

Answer 212568 by unlockmath(1599) About Me  on 2010-04-21 13:45:57 (Show Source):
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Hello,
Let the width be x and the length will be 2x+8. Now the equation can be:
x+x+2x+8+2X+8=70 Are you with me so far?
Combine terms to get and subtract 16 from both sides:
6x=54 Divide 6 into both sides to get:
x=9 feet There's the width---I'll let you figure out the length.
RJ
Get the book I wrote on the basics of math at:
www.math-unlock.com


Parallelograms/294654: I need to find the area of a parallelogram with a base of 30 cm. I have to find the height of 30 60 90 triangle. The sides of the parallelogram are 30 cm and 20 cm
1 solutions

Answer 212448 by unlockmath(1599) About Me  on 2010-04-21 00:01:08 (Show Source):
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Hello,
There are 2 possible answers, depending on how the 30-60-90 triangle is set in the parallelogram.
Since we know the area is equal to base times height, the height is found by the 30-60-90 formula. It's either 10 cm or 10 sqrt3 cm
So if the height is 10 the area would be:
300 sq cm or
300 sqrt3
RJ
www.math-unlock.com


Inequalities/294664: Solve each inequality. 1/x is greater than or equal to 4x
1 solutions

Answer 212445 by unlockmath(1599) About Me  on 2010-04-20 23:32:47 (Show Source):
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Hello,
Let's write this (1/x is greater than or equal to 4x) as:
1/x >= 4x Multiply by x on both sides to get:
1>=4x^2 Divide by 4 and then square root both sides to get:
+-1/2>=x
There we go.
Make sense?
RJ Check out a book at:
www.math-unlock.com


Rectangles/294662: the perimeter of a rectangle is 114 feet. Its length is three more than twice its width. What is the dimensions of the rectangle?
1 solutions

Answer 212443 by unlockmath(1599) About Me  on 2010-04-20 23:25:12 (Show Source):
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Hello,
Let's have "x" be the width and "2x+3" represent the length so we can set up the following equation:
x+x+2x+3+2x+3=114 Combine like terms to get:
6x+6=114 Subtract 6 divide by 6 both sides to get:
x=18 feet
I'll let you figure out the length.
Make sense?
RJ I wrote a book you should check out:
www.math-unlock.com


logarithm/294482: Log base 5 (r+2) + log base 5 (r-2) = 1

log base 3 (a-3) = 1 + log base 3 (a+1)
log exponent 2x = (log x exponent 2
Thanks
1 solutions

Answer 212325 by unlockmath(1599) About Me  on 2010-04-20 16:36:30 (Show Source):
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Hello,
I'll help you out with the first one (Log base 5 (r+2) + log base 5 (r-2) = 1)
This can be rewritten as:
Log base 5 (r+2)(r-2) = 1
Now let's exponentiate both sides by using base 5 to get:
5^log5(r+2)(r-2)=5^1 This can then be written as:
(r+2)(r-2)=5 Expand this out to get:
r^2-4=5 Add 4 to both sides to get:
r^2=9 Square root both sides will result in:
r=+-3
Make sense?
RJ
www.math-unlock.com


Expressions-with-variables/294481: Do the operation and simplify the answer.
%285x%5E2%2B21x%2B4%29%2F%28x%5E2-16%29 / %285x%2B1%29%2F%28x-2%29
I need help with this please.
1 solutions

Answer 212308 by unlockmath(1599) About Me  on 2010-04-20 16:08:31 (Show Source):
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Hello,
This %285x%5E2%2B21x%2B4%29%2F%28x%5E2-16%29 / %285x%2B1%29%2F%28x-2%29 can be written as follows:
{(5x^2+21x+4)/(x^2-16)} multiplied by {(x-2)/(5x+1)} The first fraction can be rewritten as:
{(5x+1)(x+4)/(x-4)(x+4)}times{(x-2)/(5x+1)} Notice the (5x+1) and the (x+4)cancels out to leave us with:
(x-2)/(x-4)
Make sense?
RJ
There's a book I wrote on the basics you'd like:
www.math-unlock.com


Rectangles/294477: in a rectangle measure the primeter to the nearest 1/2 inch cm

1 solutions

Answer 212305 by unlockmath(1599) About Me  on 2010-04-20 15:57:23 (Show Source):
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This makes no sense. Did you forget part of the problem?
RJ


Quadratic_Equations/294235: ∛(-64) compute the following
1 solutions

Answer 212235 by unlockmath(1599) About Me  on 2010-04-19 23:10:56 (Show Source):
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Hello,
What we need to do is find a negative number that would be multiplied by itself 3 times to get -64. Any idea.
Try -4
RJ
There's a book I wrote on the basics of math, check it out at:
www.math-unlock.com


Quadratic_Equations/294240: t^2+6t+8=0 find the root of the quadratic equation, if more than 1 root separate by a comma
1 solutions

Answer 212233 by unlockmath(1599) About Me  on 2010-04-19 23:07:04 (Show Source):
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Hello,
t^2+6t+8=0
We can factor this as:
(t+4)(t=2)=0
Solve for t to get:
t=-4
t=-2
There you go!
Make sense?
RJ
www.math-unlock.com


Problems-with-consecutive-odd-even-integers/293897: The product of two consecutive positive even integers is one hundred sixty-eight. Find the two integers.

1 solutions

Answer 212057 by unlockmath(1599) About Me  on 2010-04-19 12:40:25 (Show Source):
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Hello,
Let's show the numbers as "x" and "x+2" then we can solve this as:
x(x+2)=168 Subtract 168 from both sides to get:
x^2+2x-168=0
Now factor this:
(x-12)(x+14)=0 Now solve x to get:
x=12
x=-14
Obviously the only positive number would be:
12 and the other number is 14
Make sense?
RJ
There's a book I wrote on the basics of math:
www.math-unlock.com


Quadratic_Equations/293896: I need help in factoring this equation! I also need it to be shown to me step by step because I dont know how to solve it!
+2x%5E3-x%5E2-18x%2B9=0+
1 solutions

Answer 212056 by unlockmath(1599) About Me  on 2010-04-19 12:31:29 (Show Source):
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Hello,
Let's first off regroup this 2x^3-x^2-18x+9=0 to give us:
x^2(2x-1)-9(2x-1)=0 From this we have (2x-1) being multiplied by x^2 and -9 so we can use the distributive property to rewrite this as:
(x^2-9)(2x-1)=0 We can factor (x^2-9) to get the following:
(x-3)(x+3)(2x-1)=0 Are you with me so far?
Now we can solve for x to get:
x=3
x=-3
x=1/2
Of course, to check if these are correct, just plug them into the original equation.
Make sense?
RJ
Check out a book I wrote.
www.math-unlock.com


Evaluation_Word_Problems/293502: A 12-lb puupy is gaining weight at 2/3lb per week. How much more time will it take for the puppy's weight to exceed 37 2/3 lb?
1 solutions

Answer 211856 by unlockmath(1599) About Me  on 2010-04-18 14:20:38 (Show Source):
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Hello,
Let's have "x" be the time involved so the equation would be:
2/3(x)+12>113/3 Multiply both sides by 3 to get:
2x+36>113 Subtract 36 from both sides to get:
2x>77 Divide by 2 to get:
x>38.5 weeks
Make sense?
RJ
There's a book I wrote that that might help:
www.math-unlock.com


Geometric_formulas/293434: A clay model of an automobile is 8 inches and weighs 2 pounds, what would a full-size model weigh if it were 12 feet?
1 solutions

Answer 211843 by unlockmath(1599) About Me  on 2010-04-18 11:56:01 (Show Source):
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Hello,
We can set up a proportion as follows: (hint: we need to have both be the same measurements, either feet or inches)
8/2=144/x Cross multiply to get:
x=36 pounds
Make sense?
There's a book I wrote that will give you the basics of math:
www.math-unlock.com


Linear_Equations_And_Systems_Word_Problems/293438: Tickets for a show cost $6.00 for adults and $4.50 for children. 400 tickets were sold for a total of $2100. How many adult tickets and how many childrens tickets were sold?
1 solutions

Answer 211841 by unlockmath(1599) About Me  on 2010-04-18 11:45:22 (Show Source):
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Hello,
We can set up 2 equations and solve it from there. Let "x" be adults and "y" represent children.
x+y=400
6x+4.5y=2100
Multiply the first equation by -6 and add it to the second equation:
-6x-6y=-2400
6x+4.5y=2100
This will give us:
-1.5y=-300 Divide each side by -1.5 to get:
y=200 children tickets. Now plug this into the first equation to find x:
x=200 adult tickets
Make sense?
Get a book I wrote on the basics of math at:
www.math-unlock.com


Probability-and-statistics/293441: how many different ways can a researcher select three mice from 15 mice and assign them each to a different test?
thank you!
1 solutions

Answer 211835 by unlockmath(1599) About Me  on 2010-04-18 11:34:55 (Show Source):
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Hello,
The formula is nPr=n!/(n-r)!
So it would look like this:
15!/(15-3)! This expands out to:
(15x14x13x12x11x10x9x8x7x6x5x4x3x2x1)/(12x11x10x9x8x7x6x5x4x3x2x1)
I'll let you do the calculations from here.
Make sense?
RJ
www.math-unlock.com


Equations/293011: 3x/4-3=x/2+2
1 solutions

Answer 211533 by unlockmath(1599) About Me  on 2010-04-16 15:46:15 (Show Source):
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Hello,
With this 3x/4-3=x/2+2 let's first get rid of the fractions by multiplying both sides by 4 to get:
3x-12=2x+8 Now we can add 12 and subtract 2x from both sides to get:
x=20
Make sense?
RJ
There's a book I wrote you should get:
www.math-unlock.com


Quadratic_Equations/293032: Find the value of x. If necessary, round to the nearest tenth
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This is the way I'm thinking to solve it.
sqrt(28) = 5.2915
Rounded 5.3
5.3*5.3 = 28.09...rounded to 28.
Is that how I would solve it?
1 solutions

Answer 211530 by unlockmath(1599) About Me  on 2010-04-16 15:32:02 (Show Source):
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Hello,
Yes, you got the right idea but missed an important value. Let's do step by step so it's clear.
We know the area of a triangle is 1/2(base x height) so we can plug in the values known as:
28=x(x)(1/2) Or rewritten as:
28=x^2/2 Multiply each side by 2 to get:
56=x^2 Square root each side to get:
x=sqrt 56 Or
x=7.48 inches (rounded off)
RJ
Check out a book I wrote on the basics of math at:
www.math-unlock.com


Linear-equations/291743: (-9,3)(-8,-3)

1 solutions

Answer 210899 by unlockmath(1599) About Me  on 2010-04-13 14:54:32 (Show Source):
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Hello,
You better ask what you want done with these two points. Slope? Equation?
RJ