How do you find the multiplier of a percentage increase or percent decrease?

Answer 1

By 'multiplier', I'm assuming you mean the decimal by which you are going to multiply the number to get the answer. If you didn't understand that, then I hope you'll understand the explanation below;

You want 90% of 100. You can do this in your head, so you can use your answer to double check mine in a moment.

90% simply means 90 in every 100, which can be written as a fraction: 90/100 (90 over 100).

Next step; simplify the fraction. It simplifies to a decimal: 0.9.

Tap it into your calculator, multiply by 100 and you have the answer you expected; 90.

The general rule is to divide by 100. In primary school, I was always taught that to multiply by 10, you add a 0 onto the end, by 100 add two. In secondary school, it becomes 'move the number two places to the left', so the rule is applied in the opposite direction for division. Division by 100 means that you knock two 0's off, or move the number two places to the right.

This means that the 90 from earlier has moved one to become 9.0, then another to become 0.90.

It's the same for an increase. An increase of 10% means that you want 110% of the original. Again, we will use 100;

110% of 100 can again be done in your head.

Now apply the rule; move the number two places to the right and you get 1.10.

Now multiply 100 by 1.1. The answer is 110.

An arbitrary example;

56% of 56

0.56 * 56 = 31.36

Incidentally, you may be looking for something else if you're wondering about working out percentages.

If you scored 36 out of 60 on a test, how well did you do?

I'll take you through it.

As a percentage, 87 out of 100 is 87%. 87 out of 100 can also be written as 87/100 (87 over 100)

That fraction simplifies to 0.87. Using the inverse of what we were doing before, 0.87 = 87%

If we apply this to our problem, we can find the percentage by substituting our numbers into the place of the 87 and 100.

36/60 = 0.6 = 60%

If you're wondering why I added this in, it's because it's closely related and somewhat more useful than the preceding content.