5. Calculating percentages
Calculating percentages
In general, when calculating percentages, the percentages must first be converted to fractions or decimals. A percentage value can be calculated from a number by multiplying the base value by a percentage factor.
Example 1
How much is [[$ 20 \: \% $]] from the number [[$ 150 $]]?
Example 2
A pair of jeans shrinks by [[$ 3 \: \% $]] the first time they are washed. How much shorter will the jeans be after the first wash if their original length was [[$ 98 \: \text {cm} $]]?
Solution:
[[$ \displaystyle\frac {3} {100} \cdot 98 \: \text {cm} = 0,03 \cdot 98 \: \text {cm} ≈ 2,9 \: \text {cm} $]]
Answer: The jeans will shrink by [[$ 2,9\: \text {cm} $]].