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triangle

by vaivish » Wed Jun 25, 2008 10:08 am
1) Right triangle PQR is to be constructed in xy-plane so that the right angle is at P and PR is parallel to X-axis. The x and y-coordinates of P, Q, R are to be integers that satisfy the inequalities -4<=x<=5 and 6<=y<=16. How many different triangles with these properties could be constructed?

A) 110
B) 1,100
C) 9,900
D) 10,000
E) 12,100
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by egybs » Wed Jun 25, 2008 10:54 am
Heh, i just did this one the other day.

We basically need to pick two points that satisfy x, and two points that satisfy y.

Since there are 10 possible values for x: we do 10*9 and since there are 11 possible values for y we do 11*10.


Multiply those all together, and you get 11*9*10*10 = 99*100 = 9900

C.

If you need more explanation, i'm happy to help.
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by parallel_chase » Tue Jul 08, 2008 10:22 am
egybs wrote:Heh, i just did this one the other day.

We basically need to pick two points that satisfy x, and two points that satisfy y.

Since there are 10 possible values for x: we do 10*9 and since there are 11 possible values for y we do 11*10.


Multiply those all together, and you get 11*9*10*10 = 99*100 = 9900

C.

If you need more explanation, i'm happy to help.
Hi I would like to know why did multiply 10*9 and 11*10.

I know that there are 10 values of X and 11 values of Y. But just cant understand the product part.

Thanks
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