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Lesson · Grade 6 · Mathematics

Finding the Whole or the Percent When One Is Missing

  • Grade 6
  • Mathematics
  • 1 min 7 s
  • British Columbia
  • BC6-MA-19

To answer "8 is 20% of what number?", a bar for the whole (100%) is split into ten 10% parts: the 2 shaded parts make 8, so each part is 4 and the whole is 10 × 4 = 40. The answer is checked by finding the percent from the part and the whole (8 ÷ 40 = 0.2, which is 20%), and the video ends on a recap: find 10% first, then multiply by 10.

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In one sentence

The question this lesson answers

8 is 20 percent of what number?

We know the part and the percent, but the whole is missing.

Transcript

What the lesson says

8 is 20 percent of what number?

We know the part and the percent, but the whole is missing.

Draw a bar for the whole, which is 100 percent.

Split it into 10 equal parts, so each part is 10 percent.

20 percent is 2 parts, and together they make 8.

8 divided by 2 is 4, so each 10 percent part is 4.

10 parts of 4 make 40, so the whole is 40.

So 8 is 20 percent of 40.

To check, ask what percent of 40 is 8.

Divide the part by the whole: 8 divided by 40 is 0.2.

0.2 is 20 hundredths, which is 20 percent.

That matches the 20 percent we started with, so 40 is right.

To find the whole, work out 10 percent first, then multiply by 10.

Curriculum

Where this fits

British Columbia, Grade 6

Mathematics, Number: whole-number percents and percentage discountsBC6-MA-19

Previous: Percent of an AmountNext: Discount and Sale Price

The outcomes and strands follow the British Columbia curriculum.

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