100% of an amount is the same value as the original amount.

103% is `frac(103)(100)` = 1.03 times larger than the original amount.

The number 1.03 is known as a **multiplier**.

To calculate a multiplier increase, divide the percentage by 100 (to make it a decimal), then add it to 1. Multiply this against the original amount:

Increase 80 by 5%

Multiplier = 1 + `frac(5)(100)` = 1.05

Calculation = 80 x 1.05 = 84

To calculate a multiplier *decrease*, divide the percentage by 100 and *subtract* from 1:

Reduce 92 by 4%

Multiplier = 1 - `frac(4)(100)` = 0.96

Calculation = 92 x 0.96 = 88.32

A brand of washing powder is being sold on a special offer. The offer states that there is an additional 30% (by weight) compared to the normal box. If the normal weight is 3200g, what weight is sold in the special offer box?

The multiplier is 1 + `frac(30)(100)` = 1.3

The new amount is 3200 x 1.3

= 4160g

Answer: 4160g

In a sale, a jacket has been reduced by 15%. If the original price of the jacket was £140, what is the sale price?

The multiplier is 1 - `frac(15)(100)` = 0.85 (it is a decrease)

= 140 x 0.85

= 119

Answer: £119

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