How to
Calculate the Percentage
Increase or Decrease
A percentage increase or decrease tells us by how much something became bigger or smaller.
Step 1
Subtract the new amount from the old amount. If the answer is negative,
you have a percentage increase, and if the answer positive you have a
percentage decrease.
Step 2
Divide the answer by the old amount.
Step 3
Multiply by
Step 4
Simplify your answer.
Step 5
Write down your answer with a % sign and say whether it is
an increase or decrease.
100
1
Example
A pair of jeans is marked down from
R500 to R350. What is the percentage
increase or decrease?
15 000 100
÷
500
100
150 5
.=
÷
5
5
30
.=
1
Step 4: =
Step 1: Old – new = R500 – R350 = R150
Step 2: Answer ÷ old =
Step 3: Multiply by
100
1
150
500
Step 5: 30% decrease in price
150 100
×
500
1
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How to Calculate the Percentage Increase or Decrease
Now answer these story sums in your workbook:
1. A farmer’s chickens used to lay 300 eggs every day. Now they lay 350 eggs every day.
What percentage increase or decrease is this?
2. There are 28 sweets in a box. Elna eats 14 of them. What percentage increase or decrease
is there in sweets?
3. On Monday, 4 315 cars drive on the highway. On Tuesday, 5 178 cars drive on the
highway. What is the percentage increase or decrease in the number of cars on the
highway?
4. Maths lessons used to be 40 minutes, but now they are 45 minutes long. What is the
percentage increase or decrease in time spent in maths lessons?
5. On a partly cloudy day, clouds cover 5km2 of the sky. When it is rainy, the clouds cover
the full 15km2 area. What percentage increase or decrease in cloud cover?
6. Last year, your school collected 800 easter eggs. This year, they collected 915 easter eggs.
What percentage increase or decrease in easter eggs did your school collect?
7. An old kettle takes 7 minutes to boil. A new kettle takes 4 minutes to boil. What is the
percentage increase or decrease in the amount of time taken to boil water?
8. When load shedding moves from stage 2 to stage 4, we go from no electricity for 4
hours a day, to no electricity for 6 hours a day. What is the percentage increase or
decrease in the number of hours without electricity?
9. A plant is 20cm tall. It grows another 15cm. What is the percentage increase or decrease
in growth?
10. In Grade 6, the end-of-year exam is out of 100 marks. In Grade 7, the end-of-year exam
is out of 120 marks. What is the percentage increase or decrease in the number of marks?
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