Potentially stupid question

[ukdave32]

Hi all,

I am one of those high verbal/low quant people, at least from first diagnostic GMAT Prep test (though my job is quant-focused and I finished top of my undergrad class in economics 6 years ago). I am in the process of working through the MGMAT guides and a lot of what I did 5-6 years ago is thankfully coming back to me! However, I was stumped the other day by something seemingly easy (so easy the MGMAT team did not explain it). For those who have MGMAT Fifth Edition of Fractions, Decimals, and Percents, I refer specifically to pag 53, solution 1 where solving for Y.

In a nutshell, I need to solve the following for Y and cannot for the life of my understand step 3 to 4 below.

1) y/100 x 120 = 48

2) y/10 x 12 = 48 ....FINE SO FAR

3) y/5 x 6 = 48 .... FINE AGAIN

4) y = 48 x 5/6 .... HUH!? I REALLY DO NOT GET HOW THE 6 MOVES UNDER THE 5

5) y = 8 x 5/1 .... FINE

6) y - 40 .... FINE

Please could someone break down the logic/process for step 3 to step 4? I have been fine with the theory but am letting myself down with inability to do the operatings once I understand how to answer the question.

This may be a "duh" question, but would help me with a roadblock.

Many thanks in advance,
David

[Armada0023]

That is kinda screwy but here's how I debugged their work:

Y/5 * 6 = 48
...multiply that 6 (really 6/1) into Y/5:
6Y/5 = 48
...multiply both sides by 5/6 to cancel out the left side:
5/6 * 6Y/5 = 48 * 5/6
...turns into:
Y = 48 * 5/6
...then solve from there.

Not at all how I would have approached it. I too, am studying from the MGMAT books and noticed a few answer solutions that stray far from the quick and easy path (probably for good reason - forcing you to learn a different way/solution).

[ukdave32]

Really appreciate the quick and helpful response! Makes sense now.

Out of curiosity, how would you handle it if doing your own way?

Cheers

[Armada0023]

I would have done the following:

Y/5 * 6 = 48
Y/5 = 48/6
Y/5 = 8
Y = 8 * 5
Y = 40

[ukdave32]

Either I was way too tired when I was trying to solve, or the MGMAT approach through me for a loop!

Thanks a lot

[Jim@StratusPrep]

You are simply multiplying both sides of the equation by 6/5