Percent of a number

Percent of a number

In this section, we will try to estimate the percent of a number without using a calculator. The trick is to breakdown the percent into smaller percent first. These smaller percentages are easier for mental calculation.


  • 1.
    Evaluate without using a calculator. Then, check your answers with a calculator.
    15% of 40

    320% of 600

    17.5% of 20

    201420\frac{1}{4}% of 50

  • 2.
    The total rain precipitation of last summer was 350 mm. If it increased by 121212\frac{1}{2}% this summer, what was the rain precipitation this summer?

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