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#1
09-04-2009, 02:01 PM
 commasense Charter Member Join Date: Mar 2003 Location: Baltimore,MD Posts: 4,989
Help with stupid simple math problem.

I think I used to know this, and I know I should be able to figure it out, but my high school math skills have atrophied over the past 40 years.

What's the method for finding factors of a given number that are in a certain ratio to each other? For instance, a movie theater screen is said to be 180 square meters in area. Assuming that its sides are in a 1.78 ratio (the width is 1.78 times the height), how do I determine their dimensions?

Thanks.

Last edited by commasense; 09-04-2009 at 02:03 PM. Reason: damn typo!
#2
09-04-2009, 02:10 PM
 Cabbage Guest Join Date: Sep 1999
Let h and w be width and height, respectively.

You're given:

hw = 180

w=1.78h

Substitute:

h(1.78h) = 1.78h^2=180

Solve for h: sqrt(180/1.78)
#3
09-04-2009, 02:10 PM
 The Hamster King Charter Member Join Date: Jun 2000 Location: Los Angeles Posts: 8,752
Area = Width x Height
Width = Height x 1.78

So, substituting the second equation into the first:

Area = Height x Height x 1.78

And solving for Height:

Height = Square Root( Area / 1.78 )
#4
09-04-2009, 02:13 PM
 Giles Charter Member Join Date: Apr 2004 Location: Newcastle NSW Posts: 11,560
If x is the shorter dimension, then

1.78 x^2 = 180

x^2 = 101.1236

x = 10.05602 metres

and the other side is 17.89972 metres.
#5
09-04-2009, 02:16 PM
 commasense Charter Member Join Date: Mar 2003 Location: Baltimore,MD Posts: 4,989

(I had that response all ready to go.)

Thanks, guys.

(Now can someone help me figure out how much 2+2 is?)
#6
09-04-2009, 02:36 PM
 Malacandra Guest Join Date: Jan 2003
How much would you like it to be?
#7
09-04-2009, 03:13 PM
 Chronos Charter Member Join Date: Jan 2000 Location: The Land of Cleves Posts: 47,968
2 + 2 = 1 modulo 3.
#8
09-04-2009, 03:30 PM
 DSYoungEsq Guest Join Date: Jul 1999
5 (for very large values of 2)

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