Theory
How do you calculate a new value after an increase?
With a percentage increase, the old value is 100%.
For example, if 15% is added, the new value becomes 115%. This corresponds to a growth factor of 1,15.
Multiply the old value by that growth factor to find the new value.
- Determine the growth factorAdd the percentage to 100% and then divide by 100.
- Multiply by the growth factorMultiply the old value by the growth factor.
You use multiplication with equal groups.
A × B means that you take the same amount B, A times.Instead of adding again and again, you calculate the product all at once.
A value of 80 increases by 15%. What is the new value?
- Determine the growth factor100% + 15% = 115%, so the growth factor is 1,15.
- Multiply by the growth factor80 × 1,15 = 92.