The petrol tank of Ben's car was 75% empty. He went to the petrol kiosk and topped up 38 ℓ of petrol. When he reached the florist, the petrol tank was 80% full. Given that he used 5 ℓ of fuel to get to the florist 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 |
+ 38 |
- 38 |
|
| Change 2 |
- 5 |
+ 5 |
|
| After |
4x4 =
16 u |
1x4 =
4 u |
5x4 =
20 u |
75% =
75100 =
34 Empty : Total = 3 : 4
80% =
80100 =
45 Full : Total = 4 : 5
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 4 and 5 is 20.
Volume of petrol in the end
= 5 u + 38 - 5
= 5 u + 33
16 u = 5 u + 33
16 u - 5 u = 33
11 u = 33
1 u = 33 ÷ 11 = 3
Capacity of the petrol tank
= 20 u
= 20 x 3
= 60 ℓ
Answer(s): 60 ℓ
