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Lesson · Grade 8 · Mathematics

Half a Percent of a Billion

  • Grade 8
  • Mathematics
  • 2 min 16 s
  • British Columbia
  • BC8-MA-06

Using a 100-square grid for one billion, the video finds 1% by dividing by 100 (10 000 000) and then halves it to get ½%, or 0.5%, which is 5 000 000. It checks the answer by writing 0.5% as the decimal 0.005, and warns against the common mistake of writing 0.5% as 0.5 or 0.05.

Concept: Percents less than 1%: half a percent of a billion

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In one sentence

The question this lesson answers

What is one half of one percent of one billion?

Percent means out of one hundred. Picture one billion as 100 equal squares. All 100 together make 100%.

Transcript

What the lesson says

What is one half of one percent of one billion?

Percent means out of one hundred. Picture one billion as 100 equal squares. All 100 together make 100%.

One square is 1 out of 100, so it is 1%. As a decimal, 1% is 1 divided by 100, which is 0.01.

Step 1: find 1% of one billion. To find 1%, divide by 100.

Here, dividing by 100 takes the last two zeros off one billion. That leaves ten million.

Check: ten million times 100 is one billion.

Now, one half percent means half of 1%. That is less than 1%, so it is half of one square.

Written with a fraction, one half percent is a fractional percent. Written with a decimal, it is 0.5%, a decimal percent.

Step 2: halve ten million. Ten million divided by 2 is five million.

Check: five million times 2 is ten million.

So one half percent of one billion is five million.

Let us check another way. 0.5% means 0.5 divided by 100, which is 0.005.

And 0.005 times one billion is five million, the same answer.

Be careful: 0.5% is 0.005. A common mistake is to write it as 0.5 or as 0.05.

But 0.5 means 50%, which would be half the billion, and 0.05 means 5%. Both are far too big.

So, to find half a percent, find 1% and then halve it. Half a percent of one billion is five million.

Curriculum

Where this fits

British Columbia, Grade 8

Mathematics, Number: percents less than 1 and greater than 100 (decimal and fractional percents)BC8-MA-06

Previous: Estimating √30 Between Two Perfect SquaresNext: Percents over 100%: more than the whole

The outcomes and strands follow the British Columbia curriculum.

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