Unit 3, Lesson 13
Benchmark Percentages
Grade 6
13.1
Warm-up
Which three go together? Why do they go together?
13.2
Activity
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How much is 50% of 10 liters of milk?
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How far is 50% of a 2,000-kilometer trip?
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How long is 50% of a 24-hour day?
- How can you find 50% of any number?
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- 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?
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- 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?
13.3
Activity
Calculate each value mentally. Be prepared to explain your reasoning.
- 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?
13.4
Activity
Han and Clare go shopping, and they each have a coupon.
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Han buys an item with a normal price of \$15, and uses a 10% off coupon. How much does he save by using the coupon? Show your reasoning.
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Clare buys an item with a normal price of \$24, but saves \$6 by using a coupon. For what percentage off is this coupon? Show your reasoning.
Student Lesson Summary
Certain percentages are easy to think about in terms of fractions.
A double number line with 5 evenly spaced tick marks. The tick marks on the top number line are labeled 0, one fourth of x, one half of x, three fourths of x, and x. The tick marks on the bottom number line are labeled 0 percent, 25 percent, 50 percent, 75 percent, and 100 percent.
- 25% of a number is always of that number. For example, 25% of 40 liters is , or 10 liters.
- 50% of a number is always of that number. For example, 50% of 82 kilometers is , or 41 kilometers.
- 75% of a number is always of that number. For example, 75% of 1 pound is pound.
- 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 always of that number, so 70% of 30 days is , or 21 days.
A double number line with 11 evenly spaced tick marks. For the top number line the number 0 is on the first tick mark, one tenth of x on the second, seven tenths of x on the eighth, and x on the eleventh. The remaining tick marks are blank. On the bottom number line starting from the first tick mark, zero percent, 10 percent, 20 percent, 30 percent, 40 percent, 50 percent, 60 percent, 70 percent, 80 percent, 90 percent, and 100 percent are labeled.
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