The petrol tank of Simon's lorry was 55% empty. He went to the petrol kiosk and topped up 17 ℓ of petrol. When he reached the bank, the petrol tank was 75% full. Given that he used 5 ℓ of fuel to get to the bank from the kiosk, find the capacity of the petrol tank.
| |
Full |
Empty |
Total |
| Before |
9x1 =
9 u |
11x1 =
11 u |
20x1 =
20 u |
| Change 1 |
+ 17 |
- 17 |
|
| Change 2 |
- 5 |
+ 5 |
|
| After |
3x5 =
15 u |
1x5 =
5 u |
4x5 =
20 u |
55% =
55100 =
1120 Empty : Total = 11 : 20
75% =
75100 =
34 Full : Total = 3 : 4
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 20 and 4 is 20.
Volume of petrol in the end
= 9 u + 17 - 5
= 9 u + 12
15 u = 9 u + 12
15 u - 9 u = 12
6 u = 12
1 u = 12 ÷ 6 = 2
Capacity of the petrol tank
= 20 u
= 20 x 2
= 40 ℓ
Answer(s): 40 ℓ
