Education.com
Try
Brainzy
Try
Plus

# Ratios, Proportions, and Percents for CBEST Exam Study Guide (page 3)

By
Updated on Mar 23, 2011

#### Practice

Try the four steps on the following problems.

1. On a blueprint, inch equals 2 feet. If a hall is supposed to be 56 feet wide, how many inches wide will the hall be on the blueprint?
1. 14
2. In a certain recipe, 2 cups of flour are needed to serve 5 people. If 20 guests are coming, how much flour will be needed?
1. 50
2. 30
3. 12
4. 10
5. 8
3. A certain district needs 2 buses for every 75 students who live out of town. If there are 225 students who live out of town, how many buses are needed?
1. 4
2. 6
3. 8
4. 10
5. 11

1. d.
2. e.
3. b.

### Percents

There are five basic types of percent problems on the CBEST. As is true with most other types of problems on the CBEST, percent problems most often appear in word-problem format. Percents can be done by using ratios or by algebra. Since ratios have just been covered, this section will explain the ratio method.

Percents can be fairly simple if you memorize these few relationships:

#### Sample Finding Part of a Whole Question

1. There are 500 flights out of Los Angeles every hour. Five percent are international flights. How many international flights leave Los Angeles every hour?

1. You are being asked to find a part of the 500 flights. The 500 flights is the whole. The percent is 5. You need to find the part. 5% is fairly small, and considering that 20% of 500 is 100, you know your answer will be less than 100.
2. The second sentence has an implied pronoun. The sentence can be rephrased "Five percent of them are international flights." Them refers to the number 500.
3. The question is How many… Use the other sentences to reconstruct the question so it includes all the necessary information. The problem is asking "5% of 500 (them) are how many (international flights)?" The question is now conveniently set up.
4. Are is the verb; 500 and 5% are on the left side of the verb and how many is on the right side. How many is all by itself, so it goes on top of the ratio in the form of a variable; 500 is next to the of, so it goes on the bottom. At this point, check to see that the part is over the whole.
5. The 5 goes over 100.
6. The two are equal to each other.
7. Solve.
8. Twenty-five international flights leave every hour.

#### Eight Success Steps for Solving Percent Problems

Feel free to skip steps whenever you don't need them.

1. Notice the numbers. Usually you are given two numbers and are asked to find a third. Are you given the whole, the part, or both ? Is the percent given ? Is the percent large or small? Is it more or less than half? Sometimes you can estimate the answer enough to eliminate some alien answers.
2. If there are pronouns in the problem, write the number to which they refer above the pronoun.
3. Find the question and underline the question word. Question words can include how much is, what is, find, etc. In longer word problems, you may have to translate the problem into a simple question you can use to find the answer.
4. Notice the verb in the question. The quantity that is by itself on one side of the verb is considered the is.
5. Place this number over the number next to the of . If a question word is next to an is or of, put a variable in place of the number in that spot. If there is no is or no of, check to see whether one is implied. See whether you can rephrase the question, keeping the same meaning, but putting in the missing two-letter word. If all else fails, check to make sure the part is over the whole.

6. Place the percent over 100. If there is no percent, put a variable over 100 .
7. Set the two fractions equal to each other.
8. Solve as you would a ratio.