Page 208 - Math Course 1 (Book 1)

Mental Math: Percents

Mo. 6

Lesson 8

MO. 6 - L8a
KEY CONCEPTS:
1. Compute mentally with percents.
Computing Percents Mentally 2. Estimate with percents.

Concept Summary

Percent-Fractions Equivalents

1 1 1 1 1 2 1
20% = 10% = 25% = 12 % = 16 % =
5 10 4 2 8 3 6

2 3 1 1 3 1 1
40% = 30% = 50% = 37 % = 32 % =
5 10 2 2 8 3 3
3 7 3 1 5 2 2
60% = 70% = 70% = 62 % = 66 % =
5 10 4 2 8 3 3

4 9 1 7 1 5
80% = 90% = 87 % = 83 % =
5 10 2 8 3 6

Find 70% of 110 mentally.
Let’s Begin 70% of 110 = of 110 Think: 70% = 7
7
10 10
1
= 77 Think: of 110 is 11.
10
Find Percent of a Number Mentally 7
So , of 110 is 77.
10
Example Answer 70% of 110 is 77

Find 50% of 46 mentally.
1 1
50% of 46 = of 46 Think: 50% = Estimate Percents
2 2
1
= 23 Think: of 46 is 23.
2
Example
Answer 50% of 46 is 23. Estimate 22% of 494.

1
22% is about 20% or
5
Find 25% of 88 mentally. 449 is about 500 Estimate is about, not exact
1 1
25% of 88 = of 88 Think: 25% =
1
4 4 of 500 is 100.
1 5
= 22 Think: of 88 is 22.
4

Answer 25% of 88 is 22. Answer
22% of 494 is about 100.

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