The petrol tank of Perry's bus was 70% empty. He went to the petrol kiosk and topped up 25 ℓ of petrol. When he reached the mosque, the petrol tank was 75% full. Given that he used 7 ℓ of fuel to get to the mosque from the kiosk, find the capacity of the petrol tank.
|
Full |
Empty |
Total |
Before |
3x2 = 6 u |
7x2 = 14 u |
10x2 = 20 u |
Change 1 |
+ 25 |
- 25 |
|
Change 2 |
- 7 |
+ 7 |
|
After |
3x5 = 15 u |
1x5 = 5 u |
4x5 = 20 u |
70% =
70100 =
710 Empty : Total = 7 : 10
75% =
75100 =
34 Full : Total = 3 : 4
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 10 and 4 is 20.
Volume of petrol in the end
= 6 u + 25 - 7
= 6 u + 18
15 u = 6 u + 18
15 u - 6 u = 18
9 u = 18
1 u = 18 ÷ 9 = 2
Capacity of the petrol tank
= 20 u
= 20 x 2
= 40 ℓ
Answer(s): 40 ℓ