Percentages

Question 1

How do you calculate percentage increase

Answer 1

If something has increased by 30% there is a % change of 130%, therefore we can multiply the new value by timsing by 1.3

Question 2

How do you calculate percentage decrease

Answer 2

If something has decreased in value by 30% the percentage change is 70%
Therefore we can multiply by 0.7

Question 3

How can we calculate an original value when given a value that has already been decreased

Answer 3

First find what the percentage decrease has been and find the % change)

Instead of multiplying by the change we divide

E.g £90 = 1/3 og price

100%-30% = 70% = 0.7

0.7y= 90
y= 90/0.7

= 128.571
=£128.57

The same can be done with an increase in price