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# Recent problems solved by 'unlockmath'

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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)   on 2010-05-01 15:53:55 (Show Source): You can put this solution on YOUR website!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 , what is the perimeter? thank you.1 solutions Answer 215027 by unlockmath(1599)   on 2010-05-01 15:40:59 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-28 23:19:17 (Show Source): You can put this solution on YOUR website!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-111 solutions Answer 214469 by unlockmath(1599)   on 2010-04-28 16:56:05 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-28 16:45:21 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-28 16:35:47 (Show Source): You can put this solution on YOUR website!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 + 241 solutions Answer 213767 by unlockmath(1599)   on 2010-04-26 12:47:26 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-26 12:39:59 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-25 01:04:23 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-24 14:10:26 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-24 14:04:40 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-21 21:48:39 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-21 13:58:56 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-21 13:45:57 (Show Source): You can put this solution on YOUR website!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 cm1 solutions Answer 212448 by unlockmath(1599)   on 2010-04-21 00:01:08 (Show Source): You can put this solution on YOUR website!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 4x1 solutions Answer 212445 by unlockmath(1599)   on 2010-04-20 23:32:47 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-20 23:25:12 (Show Source): You can put this solution on YOUR website!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 Thanks1 solutions Answer 212325 by unlockmath(1599)   on 2010-04-20 16:36:30 (Show Source): You can put this solution on YOUR website!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. / I need help with this please.1 solutions Answer 212308 by unlockmath(1599)   on 2010-04-20 16:08:31 (Show Source): You can put this solution on YOUR website!Hello, This / 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)   on 2010-04-20 15:57:23 (Show Source): You can put this solution on YOUR website!This makes no sense. Did you forget part of the problem? RJ
 Quadratic_Equations/294235: ∛(-64) compute the following1 solutions Answer 212235 by unlockmath(1599)   on 2010-04-19 23:10:56 (Show Source): You can put this solution on YOUR website!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 comma1 solutions Answer 212233 by unlockmath(1599)   on 2010-04-19 23:07:04 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-19 12:40:25 (Show Source): You can put this solution on YOUR website!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! 1 solutions Answer 212056 by unlockmath(1599)   on 2010-04-19 12:31:29 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-18 14:20:38 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-18 11:56:01 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-18 11:45:22 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-18 11:34:55 (Show Source): You can put this solution on YOUR website!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+21 solutions Answer 211533 by unlockmath(1599)   on 2010-04-16 15:46:15 (Show Source): You can put this solution on YOUR website!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 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)   on 2010-04-16 15:32:02 (Show Source): You can put this solution on YOUR website!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)   on 2010-04-13 14:54:32 (Show Source): You can put this solution on YOUR website!Hello, You better ask what you want done with these two points. Slope? Equation? RJ