The petrol tank of Luis's lorry was 75% empty. He went to the petrol kiosk and topped up 23 ℓ of petrol. When he reached the museum, the petrol tank was 80% full. Given that he used 1 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 |
+ 23 |
- 23 |
|
| Change 2 |
- 1 |
+ 1 |
|
| 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 + 23 - 1
= 5 u + 22
16 u = 5 u + 22
16 u - 5 u = 22
11 u = 22
1 u = 22 ÷ 11 = 2
Capacity of the petrol tank
= 20 u
= 20 x 2
= 40 ℓ
Answer(s): 40 ℓ
