a+b = p
a-b = q
adding the two we get 2a = p=q or a= p+q/2
now b = a-q or p+q-2q / 2 = p-q/2
ab = (p+q/2)*(p-q/2) = p^2-q^2 / 4
ans A (typo error)
VIC problem from Knewton
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
Answer is B.
I plugged in easy values.
a+b = P & a-b=q
IF:
a=5
b=3
5+3=8
5-3=2
P = 8
Q = 2
a(b)=
5(3) = 15
Plug and chug now.... usually start from bottom to top because on problems like this they want you to waste time, plugging and chugging every where and it is sometimes on the bottom, but you can easily remove some answer choices.... E is obviously removed.
I plugged in easy values.
a+b = P & a-b=q
IF:
a=5
b=3
5+3=8
5-3=2
P = 8
Q = 2
a(b)=
5(3) = 15
Plug and chug now.... usually start from bottom to top because on problems like this they want you to waste time, plugging and chugging every where and it is sometimes on the bottom, but you can easily remove some answer choices.... E is obviously removed.
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manpsingh87
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a+b=p;---------1)tonebeeze wrote:Please see attachment. Can someone walk me through the algebra. Thanks
a-b=q;----------2)
squaring equations 1 and 2 we get;
(a+b)^2=p^2;----3)
(a-b)^2=q^2;------4)
Now subtracting 3 and 4 we have
4ab=p^2-q^2;
ab= p^2-q^2/4 ;
hence A
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srcc25anu
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Yes, my mistake. its A indeed.
rohu27 wrote:option A right?
srcc25anu wrote:a+b = p
a-b = q
adding the two we get 2a = p-q or a= p+q/2
now b = a-q or p+q-2q / 2 = p-q/2
ab = (p+q/2)*(p-q/2) = p^2-q^2 / 4
ans B
