Source: Revised GRE PDF 1st Ed. Section 6: Math; #21 (p. 90)


The quantities S and T are positive and

The quantities S and T are positive and are related by the equation S = k/T, where k is a constant. If the value of S increases by 50 percent, then the value of T decreases by what percent? 25%, 33 1/3%, 50%, 66 2/3%, 75%

2 Explanations


Vish .

There is a pattern increase by 1/x% implies a decrease in (x+1)%.

I mean an increase in 50% implies a dec in T by 33.33%

similarly inc by 25% means a dec by 20%

similarly inc by 16.66% means a dec by 14.28%...

Nov 27, 2015 • Comment

Cydney Seigerman, Magoosh Tutor

Hi Vish,

Thanks for your comment :) There is definitely a pattern in this question!

However, I'm not exactly sure what (1/x%) represents. An increase of 50% is means that the new value is 1.5 times greater than the original.

It turns out that S and T are inversely proportional. In other words, S is proportional to 1/T. So, when S changes by a factor of x, then T will change by a factor of 1/x. And we can express a decrease of T as (1-1/[change in S]).

If S increases by 50% (a factor of 1.5), T will change by a factor of 1/1.5 = 2/3. The new value of T will be 2/3 of the original value, which is a decrease of 1-2/3 = 1/3 = 33.3%.

I hope this helps!

-Cydney :)

Dec 2, 2015 • Reply

Hey, vish this is fixed pattern above you mention there!

Apr 29, 2016 • Reply


Gravatar Chris Lele, Magoosh Tutor

Sep 26, 2012 • Comment

Add Your Explanation

You must have a Magoosh account in order to leave an explanation.

Learn More About Magoosh