Cracking the GRE, 2013 Edition by Princeton Review

Author:Princeton Review [Review, Princeton]
Language: eng
Format: epub
Published: 0101-01-01T00:00:00+00:00

Every Fraction Can Be a Ratio, and Vice Versa

Every ratio can be expressed as a fraction. A ratio of 1 : 2 means that there's either

1

a total of three things or a multiple of three, and the fraction means "1 out

2

of 2."

Treat a Ratio like a Fraction

Anything you can do to a fraction you can also do to a ratio. You can crossmultiply, find common denominators, reduce, and so on.

Find the Total

The key to dealing with ratio questions is to find the whole, or the total. Remember: A ratio tells us only about the parts, not the total. In order to find the total, add the numbers in the ratio. A ratio of 2 : 1 means that there are three total parts.

A ratio of 2 : 5 means that we're talking about a total of 7 parts. And a ratio of 2 :

5 : 7 means there are 14 total parts. Once you have a total you can start to do some

fun things with ratios.

For example, let's say you have a handful of pennies and nickels. If you have

Like a fraction. a ratio

30 total coins and the pennies and nickels are in a 2

expresses a relationship

: 1 ratio, how many pennies

do you have? The total for our ratio is 3, meaning that out of every 3 coins, there

between numbers.

are 2 pennies and 1 nickel. So if there are 30 total coins, there must be 20 pennies

20

2

and 10 nickels. Notice that - is the same as -1 , is the same as 2 : 1!

1 0

When you are working with ratios, there's an easy way not only to keep track of the

The minute you see the

numbers in the problem but also to quickly figure out the values in the

word "ratio," draw your

problem. lt's called the Ratio Box. Let's try the same question, but with some different

box on your scratch paper.

numbers; if you have 24 coins in your pocket and the ratio of pennies to nickels is

2 : 1, how many pennies and nickels are there? The Ratio Box for this question is

below, with all of the information we're given already filled in.

Pennies

Nickels

Total

ratio

2

1

3

multiply by

real

24

Remember that ratios are relationships between numbers, not real numbers, so

the real total is 24; that is, you have 24 actual coins in your pocket. The ratio total

(the number you get when you add the number of parts in the ratio) is 3.

Real World Math I 2 3 7

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.