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Sankofi
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 Posted: Sun Oct 05, 2008 6:24 pm Post subject: OG-11 PS 248 |
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Right Triangle PQR is to be constructed in the xy-plane so that the right angle is at P and PR is parallel to the x-axis. The x- and y-coordinates of P, Q, and 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
Please explain
OA is C |
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stop@800
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| Posted: Sun Oct 05, 2008 8:56 pm Post subject: |
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One point can be chosen in 11 ways
another in 10 ways and last one in 9 ways
so 11*10*9
9900
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aj5105
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| Posted: Sun Oct 05, 2008 9:12 pm Post subject: |
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| can you elaborate ur answer a bit more? |
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mental
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| Posted: Mon Oct 06, 2008 3:57 am Post subject: |
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| stop@800 wrote: | One point can be chosen in 11 ways
another in 10 ways and last one in 9 ways
so 11*10*9
9900 |
STOP: i suppose there was a typo
11*10*9 = 990
neways, you must have meant (11*10)*(10*9)
y can have 11 integral co-ordinates, out of that two can be chosen in 11*10 ways
x can have 10 integral co-ordinates, so two can be chosen in 10*9 ways
so total triangles = 11*10*10*9 = 9900
THIS QUESTION CAN BE FOUND IN EARLIER POSTS |
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Sankofi
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| Posted: Mon Oct 06, 2008 7:23 am Post subject: |
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| Thanks. I did a search and was not able to find, sorry. |
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