Recently while studying for the GMATs, I’ve been running into a problem specifically when it comes to quantitative questions. It is an fairly common obstacle that lots of people face: I arrive at the correct answers, but I know I take way too long to get there.

It was then that a friend referred me to GMAT Hacks.com, a website by the author of the Total GMAT books. Jeff Sackman.

There are several articles illustrating his tips and tricks on the GMATs that I have found helpful. Most recently I read a great article on doing weighted averages , problems that I was getting right but I felt like they were taking too long.

Here is a sample problem and Jeff’s explanation:

**If Jason purchased two suits for $179 each and three suits for $189 each, what is the average price Jason paid for each suit?**

**(A) $183.00
(B) $184.00
(C) $185.00
(D) $185.50
(E) $186.50**

Jeff explains that most of us would probably set up the problem like this:

(179)(2) + (189)(3)

5

…and eventually arrive at the right answer: (C), $185.00.

** Jeff’s Approach**

He writes ” Now think of a different number line: this time between 0 and 10, inclusive. If you were calculating the weighted average of 2 0’s and 3 10’s, the average would nudge toward 10. The calculations are much simpler in that case:

(0)(2) + (10)(3)

5

30 divided by 5 is 6. Again, despite the fact that we’re looking at a number line 179 points lower than the original, the weighted average is exactly 6 larger than the lower number and 4 smaller than the higher number. This is no accident. In a matter of speaking, *weighted averages don’t care what the end points are, they just care about the weights*.

By now, it may be clear how to apply this to do the example problem above more quickly. Instead of using 179 and 189 as your datapoints, use 0 and 10. Find the weighted average of 2 0’s and 3 10’s, then add 179. ”

Cue: light bulb on! Thank you, Jeff!

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