The petrol tank of Luke's sports car was 70% empty. He went to the petrol kiosk and topped up 38 ℓ of petrol. When he reached the grocery store, the petrol tank was 80% full. Given that he used 8 ℓ of fuel to get to the grocery store 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 |
+ 38 |
- 38 |
|
Change 2 |
- 8 |
+ 8 |
|
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 + 38 - 8
= 3 u + 30
8 u = 3 u + 30
8 u - 3 u = 30
5 u = 30
1 u = 30 ÷ 5 = 6
Capacity of the petrol tank
= 10 u
= 10 x 6
= 60 ℓ
Answer(s): 60 ℓ