Percentages » Percentages using ratio tables

To calculate from numbers to percentages and vice versa you can follow these steps:

1. Make a ratio table with the amount at the top and the percentages at the bottom.
2. Write all the useful numbers that are given in the table. Underneath the total you always write 100%.
3. Find out what you need to do to get to your answer. Calculate using 1!
4. Calculate the percentage or the unknown number.

Below you can find two examples. In the first the percentage is calculated and in the second the amount is calculated.

Example 1

If you get a reduction of 369 euros on a washing machine of 1230 euros, what percentage is the reduction?

: 1230
pijl half rond
× 369
pijl half rond
euros 1230 1 369
percentage 100 ... 30
pijl half rond
: 1230
pijl half rond
× 369

Calculation: 100 : 1230 × 369 = 30%

Example 2

How many cars are yellow when 12% of the 25 cars are yellow?

:100
pijl half rond
×12
pijl half rond
number of cars 25 ... 3
percentage 100 1 12
pijl half rond
:100
pijl half rond
×12

Calculation: 25 : 100 × 8 = 3 yellow cars

Example 3

A tv costs 484 euros including 21% VAT. What is the cost of the tv excluding VAT?

:121
pijl half rond
×100
pijl half rond
euros 484 ... 400
percentage 121 1 100
pijl half rond
:121
pijl half rond
×100

Calculation: 484 : 121 × 100 = 400 euros