KnowledgeMadeFun, home

Lesson · Grade 8 · Mathematics

Percents over 100%: more than the whole

  • Grade 8
  • Mathematics
  • 2 min 9 s
  • British Columbia
  • BC8-MA-07

Bars of 40 build up 100%, 200% and 250% of 40, and adding the bars gives 40 + 40 + 20 = 100, which matches 250% = 2.5 and 2.5 × 40 = 100. A plant that grows from 20 cm to 30 cm, which is 150% of its starting height, shows the idea in real life; the video then corrects the mistake that a percent can never be more than 100 and ends on the recap "250% of 40 = 2.5 × 40 = 100".

Anyone can watch two lessons on the website without an account. Signing in is free, no payment and no card, and opens three a day; Plus has no limit.

Loading

Share to Google Classroom

In one sentence

The question this lesson answers

What is 250 percent of 40?

Percent means per hundred. So 100 percent is the whole amount.

Transcript

What the lesson says

What is 250 percent of 40?

Percent means per hundred. So 100 percent is the whole amount.

Here the whole is 40. One full bar is 100 percent of 40, which is 40.

Add a second bar of 40. Two whole bars are 200 percent of 40, which is 80.

Half of 40 is 20, so add half a bar. Two and a half bars make 250 percent.

Add the parts: 40, plus 40, plus 20, makes 100.

To do it in one step, write the percent as a decimal: 250 divided by 100 is 2.5.

Here, the word "of" means multiply, so 2.5 times 40 is 100.

Both ways give 100, which is more than the whole, 40.

Here is a real case. A plant grew from 20 centimetres to 30 centimetres.

Its starting height, 20 centimetres, is the whole, so it is 100 percent.

Its new height is 150 percent of that. 150 percent is 1.5, and 1.5 times 20 is 30 centimetres.

Check: the whole 20 centimetres, plus half of it, 10 centimetres, makes 30.

A common mistake is thinking a percent can never be more than 100. That is not true.

A part of one whole, like the share of a class that is present, stops at 100 percent.

But a new amount compared with the whole can go past 100 percent, like the plant at 150 percent.

So a percent over 100 means more than the whole: 250 percent of 40 is 2.5 times 40, which is 100.

Curriculum

Where this fits

British Columbia, Grade 8

Mathematics, Number: percents less than 1 and greater than 100 (decimal and fractional percents)BC8-MA-07

Previous: Half a Percent of a BillionNext: Percent increase: finding the new amount

The outcomes and strands follow the British Columbia curriculum.

Keep going

More on this topic