Lesson 13Benchmark Percentages
Learning Goal
Let’s contrast percentages and fractions.
Learning Targets
When I read or hear that something is 10%, 25%, 50%, or 75% of an amount, I know what fraction of that amount they are referring to.
Lesson Terms
- percent
- percentage
Warm Up: What Percentage Is Shaded?
Problem 1
What percentage of each diagram is shaded?
Activity 1: Liters, Meters, and Hours
Problem 1
How much is 50% of 10 liters of milk?
How far is 50% of a 2,000-kilometer trip?
How long is 50% of a 24-hour day?
How can you find 50% of any number?
Problem 2
How far is 10% of a 2,000-kilometer trip?
How much is 10% of 10 liters of milk?
How long is 10% of a 24-hour day?
How can you find 10% of any number?
Problem 3
How long is 75% of a 24-hour day?
How far is 75% of a 2,000-kilometer trip?
How much is 75% of 10 liters of milk?
How can you find 75% of any number?
Activity 2: Nine Is …
Problem 1
Explain how you can calculate each value mentally.
9 is 50% of what number?
9 is 25% of what number?
9 is 10% of what number?
9 is 75% of what number?
9 is 150% of what number?
Activity 3: Matching the Percentage
Problem 1
Match the percentage that describes the relationship between each pair of numbers. One percentage will be left over. Be prepared to explain your reasoning.
7 is what percentage of 14?
5 is what percentage of 20?
3 is what percentage of 30?
6 is what percentage of 8?
20 is what percentage of 5?
4%
10%
25%
50%
75%
400%
Are you ready for more?
Problem 1
What percentage of the world’s current population is under the age of 14?
How many people is that?
How many people are 14 or older?
Lesson Summary
Certain percentages are easy to think about in terms of fractions.
25% of a number is always
of that number.
For example, 25% of 40 liters isor 10 liters. 50% of a number is always
of that number.
For example, 50% of 82 kilometersor 41 kilometers. 75% of a number is always
of that number.
For example, 75% of 1 pound ispound. 10% of a number is always
of that number.
For example, 10% of 95 meters is 9.5 meters.We can also find multiples of 10% using tenths.
For example, 70% of a number is alwaysof that number, so 70% of 30 days is or 21 days.