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Section 6
Page 23
SkillsDMC ©
Percentages
Per cent (%) means out of 100 and is a way
of expressing a proportion. For example 10%
means 10 out of 100.
Knowing how to convert a number into a
percentage is a very important skill to have. It is
relatively easy to perform.
Use the following formula to convert into a
percentage.
To find a percentage of a number, multiply the
number by the percent and divide by 100.
Example:
To determine 15% of 520 kg:
1.
Multiply 520 kg with 15, which gives you
7800 kg
2.
Divide 7800 kg by 100, and you get 78 kg
3.
The answer – 78 kg is 15% of 520 kg
Mathematically this can be shown as:
15% of 520 kg = 520 kg x 15 ÷ 100 = 78 kg
Adding a percentage to a number
To add a percentage to a number, first work out
the per cent then add it on.
Example:
I’ve worked out that I need 120 trees to cover
an area. I want to add 10% extra to allow
for variables. How many trees would this be
altogether?
10% of 120 = 120 x 10 ÷ 100 = 12
So altogether I need 120 + 12 = 132 trees