1. Inverse Proportion Monday, 25 February 2019
Unitary Methods
Inverse Proportion
Monday, 25 February 2019

2. Example
If 6 men can build a wall in 8 hours, how long will it take 4 men?
6 men = 8 hours
1 man =
8 x 6
= 48 hours 48
4 men =
= 12 hours 4

3. Example
A farmer has enough hay to feed 8 sheep for 5 days.
How long would the hay last for
2 Sheep?
10 Sheep?
8 Sheep = 5 days
1 Sheep =
8 x 5
= 40 days 40
(a) 2 Sheep =
= 20 days 2 40
(b) 10 Sheep =
= 4 days 10

4. Example
A factory is painted by 12 men in 6 days.
How long would it have taken with 8 men?
12 men = 6 days
1 man =
12 x 6
= 72 days 72
8 men =
= 9 days 8

5. Example
A group of 7 people can complete a task in 12 minutes.
How long would it take 4 people?
7 people = 12 minutes
1 person=
7 x 12
= 84 minutes 84
4 people =
= 21 minutes 4