The petrol tank of Charlie's car was 70% empty. He went to the petrol kiosk and topped up 12 ℓ of petrol. When he reached the park, the petrol tank was 80% full. Given that he used 2 ℓ of fuel to get to the park from the kiosk, find the capacity of the petrol tank.
| |
Full |
Empty |
Total |
| Before |
3x1 =
3 u |
7x1 =
7 u |
10x1 =
10 u |
| Change 1 |
+ 12 |
- 12 |
|
| Change 2 |
- 2 |
+ 2 |
|
| After |
4x2 =
8 u |
1x2 =
2 u |
5x2 =
10 u |
70% =
70100 =
710 Empty : Total = 7 : 10
80% =
80100 =
45 Full : Total = 4 : 5
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 10 and 5 is 10.
Volume of petrol in the end
= 3 u + 12 - 2
= 3 u + 10
8 u = 3 u + 10
8 u - 3 u = 10
5 u = 10
1 u = 10 ÷ 5 = 2
Capacity of the petrol tank
= 10 u
= 10 x 2
= 20 ℓ
Answer(s): 20 ℓ
