Percentages

It’s almost a guarantee that there will be multiple questions on the GED math test which will test your understanding of percents (often represented by the symbol %). The first thing you should know about percents is that, although they might look like whole numbers, they almost always represent a part of a whole, just like fractions and decimals.

For example, a credit card’s interest rate (APR) might be 11%. Although 11 is a whole number 11% is actually equal to 0.11. So if you borrowed $500 on your credit card, to calculate the amount you owe in interest, 11%, just multiply 500 by 0.11, which is 55. You would owe $55 dollars in interest.

11%, as we said, is equal to 0.11. You could also write 11% as a fraction: 11/100. When you change a percent to a fraction, the denominator will always be 100. This is because percents always represents parts of one hundred. The table below illustrates how the same values can be represented by percentages, fractions and decimals.

 

Source: http://www.math4ged.com/percents/

 

Word Problems with Percents

All word problems that involve percents require you to do one of three basic things.

1. Find the percent of a number

e.g. What is 25% of 44?

2. Find what a number is when you are given a percent of it

e.g. 18 is 35% of what number?

3. Find what percent a number is of another number

e.g. 40 is what percent of 95?

The way to set all of these problems up is to write two fractions. The fraction on the left side has the part of the whole (not the percent) as the numerator, and the amount of the whole as the denominator. The fraction on the right side has the percent as the numerator and 100 as the denominator. The value you don’t know and are solving for can be represented by x.

When you set up the example question for the first type of question above it will look like:

The example for number two:

Number three:

Now you cross multiply and solve for x.

For example the way you would do number one is:

So 25% of 44 is 11.

Multi-step Problems

Many times you will have to do a calculation unrelated to percentage before you do the calculation related to percent in order to arrive at the correct answer. It won’t be very complicated, but you need to pay attention to the wording of the question.

Here’s an example question:

A trip from City A to City B costs $75 in gas and tolls. The toll fees add up to $4.50. The gas for a trip from City B to City C costs 30% more, but there are no tolls. How much will the gas cost for a trip from City B to City C?

Of course when you answer the question the first thing you should do is the precalculation of removing the toll cost. This will enable you to arrive at the correct answer since there are no tolls in the second trip.

The cost of gas for a trip from City B to City C is $91.65  .

Percent Change

If a question on the GED math test asks you to find a percent change (the percentage something increases or decreases by), all you need to do is divide the amount of change by the original amount.

Example question:

Your new apartment is 900 square feet and your old apartment was 750 square feet. How much larger is your new apartment percentage-wise?

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First you find the difference:

Then you divide the difference amount by the original amount:

Then all you need to do is convert the result of the division to a percent:

.2 = 20%

Helpful Links:

  1. Adult Education Tutor Support: Teaching Percentages http://www.eastsideliteracy.org/tutorsupport/Math/Math_Percent.htm

  2. Basics of a Percent http://www.homeschoolmath.net/teaching/percent/percent.php

  3. Percentages (exhaustive packet with explanations and worksheets) http://www.valbec.org.au/building-strength-with-numeracy/docs/Percentages-Full.pdf

  4. Percentages (%) (very basic but straightforward) https://www.mathsisfun.com/percentage.html

Worksheet Links:

  1. Percent Worksheets http://www.math-aids.com/Percent/

  2. Percentage Worksheets http://www.homeschoolmath.net/worksheets/percentages-words.php

  3. Printable Calculating Percentages Worksheets http://www.helpingwithmath.com/by_subject/percentages/per_worksheets_activities.htm

  4. Percents Worksheets https://www.math-drills.com/percentsworksheets.php

  5. Percents Worksheets http://www.commoncoresheets.com/Percent.php