The petrol tank of Jeremy's sports car was 80% empty. He went to the petrol station and topped up 49 ℓ of petrol. When he reached the mall, the petrol tank was 85% full. Given that he used 10 ℓ of fuel to get to the mall from the kiosk, find the capacity of the petrol tank.
|
Full |
Empty |
Total |
Before |
1x4 = 4 u |
4x4 = 16 u |
5x4 = 20 u |
Change 1 |
+ 49 |
- 49 |
|
Change 2 |
- 10 |
+ 10 |
|
After |
17x1 = 17 u |
3x1 = 3 u |
20x1 = 20 u |
80% =
80100 =
45 Empty : Total = 4 : 5
85% =
85100 =
1720 Full : Total = 17 : 20
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 5 and 20 is 20.
Volume of petrol in the end
= 4 u + 49 - 10
= 4 u + 39
17 u = 4 u + 39
17 u - 4 u = 39
13 u = 39
1 u = 39 ÷ 13 = 3
Capacity of the petrol tank
= 20 u
= 20 x 3
= 60 ℓ
Answer(s): 60 ℓ