From Advanced GMAT Quant

[eybrj2]

In the workout set,

Q 41.

What's wrong with this solution?

(47)(49)

(48-1)(48+1)/8 = (48^2 - 1^2)/8

= 48^2/8 - 1^2/8

Remainder of the red part is 0 and ramainder of the blue part is 1
Thus, total remainder is 1.

Q.48 If (x +y)^2 = 16 and x^2 - y^2 = 16, what is the value of 2x^2?

This is how I solved this problem, but it is different from the explanation in the book. So I'd like to check whether my solution is valid.

(x+y)^2 = 16

x + y = 4 or -4

x^2 -y^2 = 16
(x+y)(x-y) =16

if x+y = 4, x-y = 4 => combine these two 2x = 8 => x=4
if x+y = -4, x-y = -4 => combine these tow 2x = -8 => x=-4

both 4 and -4 have the some result, which is 32.

[jnelson0612]

In the workout set,

Q 41.

What's wrong with this solution?

(47)(49)

(48-1)(48+1)/8 = (48^2 - 1^2)/8

= 48^2/8 - 1^2/8

Remainder of the red part is 0 and ramainder of the blue part is 1
Thus, total remainder is 1.

Q.48 If (x +y)^2 = 16 and x^2 - y^2 = 16, what is the value of 2x^2?

This is how I solved this problem, but it is different from the explanation in the book. So I'd like to check whether my solution is valid.

(x+y)^2 = 16

x + y = 4 or -4

x^2 -y^2 = 16
(x+y)(x-y) =16

if x+y = 4, x-y = 4 => combine these two 2x = 8 => x=4
if x+y = -4, x-y = -4 => combine these tow 2x = -8 => x=-4

both 4 and -4 have the some result, which is 32.

Question #48 looks great! I like your solution. That is very similar to how I would think it through. There are often many good ways to solve these problems.

For Question #41, will you please post the original question? Posting the original question is one of our forum guidelines. :-) Then we'll be happy to help you. Thanks!