Came across this last night taking a GMATPrep -
(1001^2 - 999^s) / (101^2 - 99^2)
I know I am missing something simple here...
Choices are -
10
20
40
80
100
Answer - 10
Can someone educate me on the simple way to solve this?
Thanks In Advance! ~Sam
One I am having trouble with...
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I assume here that 999^s is wrong, instead it is 999^2
Here is how I solved it
[(1000+1)^2 - (1000-1)^2]/[(100+1)^2 - (100-1)^2]
you end up with 4000/400 = 10
However I would like to know if there is a easier way to solve this?
Here is how I solved it
[(1000+1)^2 - (1000-1)^2]/[(100+1)^2 - (100-1)^2]
you end up with 4000/400 = 10
However I would like to know if there is a easier way to solve this?
- gabriel
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First things first .. this should be in the PS section .. so moved to the PS section
An easier way to solve this is to use the formula (a^2-b^2) = (a-b)(a+b)
So, 1001^2-999^2 = (1001+999)(1001-999) = 2000*2 and 101^2-99^2 = (101+99)(101-99) = 200*2
Therefore (1001^2-999^2)/(101^2-99^2) = 4000/400 = 10 ..
An easier way to solve this is to use the formula (a^2-b^2) = (a-b)(a+b)
So, 1001^2-999^2 = (1001+999)(1001-999) = 2000*2 and 101^2-99^2 = (101+99)(101-99) = 200*2
Therefore (1001^2-999^2)/(101^2-99^2) = 4000/400 = 10 ..
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