Cracking The SAT Premium

The correct answer is (D), $993.

What Percent of What Percent of...Yikes!

Sometimes you may find successive percentage problems in which you aren’t given actual numbers to
work with. In such cases, you need to plug in some numbers.

Here’s an example:

17.A    number  is  increased   by  25  percent and then    decreased   by  20  percent.    The result  is

what    percent of  the original    number?

A) 80

B) 100

C) 105

D) 120

Careful!

Number  17  is  a   tricky

question.   Beware  of

percentage  change

problems    in  the later

questions.  The answers

to  these   problems    almost

always  defy    common

sense.  Unless  you are

careful,    you may fall    for

a   trap    answer.

Here’s How to Crack It

You aren’t given a particular number to work with in this problem’just “a number.” Rather than trying to
deal with the problem in the abstract, you should immediately plug in a number to work with. What
number would be easiest to work with in a percentage problem? Why, 100, of course.

1. 25 percent of 100 is 25, so 100 increased by 25 percent is 125.


2. Now you have to decrease 125 by 20 percent; 20 percent of 125 is 25, so 125 decreased by 20
   percent is 100.


3. 100 (our result) is 100 percent of 100 (the number you plugged in), so the answer, once again, is
   (B).

Remember: Never try to solve a percentage problem by writing an equation if you can plug in numbers
instead. Plugging in on percentage problems is faster, easier, and more accurate. Why work through long,
arduous equations if you don’t have to?