## Finding Percentage Increase and Decrease

Practice Unlimited Questions

#### Formulas for Percentage Increase and Decrease:

Percentage increase

 amount increased initial quantity
×  100%

Percentage decrease

 amount decreased initial quantity
×  100%
There are 10 children in each group below. 2 more children join Group A.

The number of children in Group A increases by 2.

Percentage increase  =
 2 10
×  100%

=   20%

There are now 20% more children in Group A than before. 3 children from Group B leave the group.

The number of children in Group B decreases by 3.

Percentage decrease  =
 3 10
×  100%

=   30%

There are now 30% fewer children in Group B than before. #### Word Problem 1: Lisa's salary was raised from \$4000 to \$4800 per month. What was the percentage increase in her monthly salary? Percentage increase  =
 \$800 \$4000
×  100%

=   20%

The percentage increase in her monthly salary was 20%.

#### Word Problem 2: The price of a chair was reduced from \$270 to \$189 in a sale. Find the percentage discount on the chair. Decrease in price  =  \$270  −  \$189

=   \$81

Percentage decrease  =
 \$81 \$270
×  100%

=   30%

The percentage discount on the chair was 30%.

#### Word Problem 3: Joey had a leaky water bottle that leaked 15 ml of water every 10 minutes. What was the percentage decrease in the water in the bottle 1 hour after the bottle was filled up to 450 ml? 10 minutes  →  15 ml

1 minute  →
 15 10
ml

60 minutes  →
 15 10
ml  ×  60

=   90 ml

After 1 hour 90 ml of water had leaked from the bottle.

Percentage decrease  =
 90 450
×  100%

=   20%

The percentage decrease in the water after 1 hour was 20%.

#### Word Problem 4: Due to some roadworks on the usual route from home to school, Peggy has to take another route to school which is 7% longer. This increase in distance is 126 m. What is the length of the new route? 7%  →  126 m

1%  →
 126 7
m

=   18 m

107%  →  18 m  ×  107

=   1926 m

The length of the new route is 1926 m.

#### Word Problem 5: Sue bought a piece of cloth 140 cm long. After washing it, the cloth shrank by 4% along its length. What is the length of the cloth now? 100%  −  4%  =  96%

96% of 140 cm  =
 96 100
×  140 cm

= 134.4 cm

The length of the cloth is 134.4 cm now.