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Lesson 5 — Activity 2: Understanding Ratios and Percents
Completion requirements
Lesson 5 — Activity 2:
Understanding
Ratios
and
Percents
Getting Ready
There are many instances in our lives where we use ratios and percents. Think about the last exam mark you got back. You know how well you did by looking at the mark on the paper. Sometimes a mark is in the form of a ratio (8/10) and sometimes it is in
the form of a percent (80%).
Try This:
In a box of 100 ice cream cones, 12 are crushed. How can you compare the number of crushed cones to the total number of cones in the box?
12/100 represents the ratio comparing the number of crushed cones to the total number of cones in the box.
Another way of comparing would be by using a percent. Since percent just means "out of 100," then 12/100 can be written as 12%. The % symbol means that the quantity was compared to 100.
Suppose you wrote a math test and got 90 out of 100 questions correct.
What percent of questions would you have answered correctly?
 90/100 is the ratio of correct answers to the total questions
 90% is the percent of correct answers
We can easily take any number out of 100 and call it a percent (or percentage).
Now think about this — what percentage did you answer incorrectly? If 90 are correct, then 100 – 90 are incorrect. Ten were marked wrong out of 100 questions.
 10/100 is the ratio of wrong answers to total answers
 10% is the percentage of wrong answers on the test
Let's try some examples!
If you got 76 questions correct out of 100 on your last science test, what percentage of questions did you answer correctly?
Let's try some examples!
If you got 76 questions correct out of 100 on your last science test, what percentage of questions did you answer correctly?
On the same test, what percentage of questions did you get wrong?
On the same test, what percentage of questions did you get wrong?

24/100 is the ratio of wrong answers to total answers(100 – 76 = 24)
 24% is the percentage of wrong answers on the test
Selfcheck!
Try this!
Try this activity to practice ratios and percents. Answer these questions on your own first. When you are finished, click on the tab below to check your answers.
Suppose you wrote a math test got 88 out of 100 questions marked correctly.
1. What would the ratio of correctly marked questions to the total questions be?
2. What would the percentage of the correct answers be?
3. What percent did you get wrong?
 Ratio of correct answers to the total number of questions would be 88/100
 The percentage of the correct answers would be 88%. (Since the total is out of 100, it can be easily changed to a percentage and will read 88%).
 The percent that was wrong would be 12%. (We first have to do a calculation where we subtract the 88 from 100. So, 100  88 = 12. Therefore, 12/100 is wrong which is 12%. )
Remember percent means "out of 100". Therefore:
 Anytime you have a number compared to 100, you can write the % symbol.
 Also, anytime you see a number with a % symbol you will know that it is out of 100
Digging Deeper
Click on the Play button below to watch a video on how to turn percents into ratios.