icedoverfire wrote:
Hi everyone,
New here. Story in brief is that I'm looking for a change in career.
Anyway -
I've been using
Magoosh GMAT prep and for the life of me my quant skills are teh suck. My career path took me as far away from math as possible (yes I know the GRE is less math intensive but I figured I'd use the harder prep to cover more stuff) -
Anyway - Here's a practice problem from
Magoosh:
If y = x + 5 and y = 12 - x and \(y^2 = x^2 + K\) then K equals which of the following:
Choices given (A) 17, (B) 25, (C) 60, (D) 119.
How is one supposed to recognize where to even begin? In the interest of getting as many approaches as possible, I won't go into what
Magoosh says to do.
Help appreciated
- ice
At first, you can start combining the first 2 equations.
12-x=x+5
2x=7
x=3.5
y=8.5
y^2 = x^2 +k
or y^2 - x^2 = k
now, this will be burdensome to calculate with decimals.
on another side, we can calculate (y-x)(y+x), which is basically y^2 - x^2.
now y-x and y+x is easier to calculate, and their product is easier to calculate as well.
y-x = 5
y+x = 12
5*12 = 60.
K is 60.
It takes time to form the number sense and start seeing the way you would approach this question.
the approach may vary, depending on how easy it is for you.