The petrol tank of Glen's car was 75% empty. He went to the petrol station and topped up 41 ℓ of petrol. When he reached the museum, the petrol tank was 85% full. Given that he used 5 ℓ of fuel to get to the museum from the kiosk, find the capacity of the petrol tank.
|
Full |
Empty |
Total |
Before |
1x5 = 5 u |
3x5 = 15 u |
4x5 = 20 u |
Change 1 |
+ 41 |
- 41 |
|
Change 2 |
- 5 |
+ 5 |
|
After |
17x1 = 17 u |
3x1 = 3 u |
20x1 = 20 u |
75% =
75100 =
34 Empty : Total = 3 : 4
85% =
85100 =
1720 Full : Total = 17 : 20
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 4 and 20 is 20.
Volume of petrol in the end
= 5 u + 41 - 5
= 5 u + 36
17 u = 5 u + 36
17 u - 5 u = 36
12 u = 36
1 u = 36 ÷ 12 = 3
Capacity of the petrol tank
= 20 u
= 20 x 3
= 60 ℓ
Answer(s): 60 ℓ