Learning Percentage Using Mental Math

There are many concrete strategies for helping students make sense of percentages. Double number lines help students understand percentages as a ratio. Models have their limits and should serve as a foundation from which students can build a deeper understanding. Eventually, students should also gain confidence in working with percents mentally.

Learning Percentage Using Mental Math:

Number Strings

Double number lines work well for a problem like finding 10% of 650 and give students a visual understanding of the problem.

After lots of practice with visual support, students should be able to mentally calculate 10% of any number. They should recognize that 10% is the same as 1/10, which is the same as dividing by 10. Dividing by 10 means a value 10 times smaller, so digits move one place value to the left.

10% of 36 is 36/10 = 3.6

Multiples of 10%

Finding 10% is important because it allows students a starting point from which to find many other values.

80% of 15 is 1.5 x 8 = 12

Multiples of 5%

Once a student has determined 10% of a number, they can simply divide that value in half to find 5%.

5% of 120 is 12/2 = 6

Combining 

35% of 80 is 8 + 8 + 8 + 4 = 28.

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Using 1%

Since 1% is 10% of 10%, students can follow a familiar pathway to find 1%.

1% of 18 is 18 div 10 div 10= 0.18

The ability to mentally calculate 10%, 5%, and 1% enables students to find virtually any percent.

41% of 250 is 25 + 25 + 25 + 25 + 2.5 = 102.5

Solving percent problems mentally will make students feel like math superstars!

Also read: How To Find Percents Using Double Number Line

Frequently Asked Questions on Percentages Using Mental Math