The petrol tank of Rael's van was 65% empty. He went to the petrol station and topped up 20 ℓ of petrol. When he reached the grocery store, the petrol tank was 80% full. Given that he used 2 ℓ of fuel to get to the grocery store from the kiosk, find the capacity of the petrol tank.
|
Full |
Empty |
Total |
Before |
7x1 = 7 u |
13x1 = 13 u |
20x1 = 20 u |
Change 1 |
+ 20 |
- 20 |
|
Change 2 |
- 2 |
+ 2 |
|
After |
4x4 = 16 u |
1x4 = 4 u |
5x4 = 20 u |
65% =
65100 =
1320 Empty : Total = 13 : 20
80% =
80100 =
45 Full : Total = 4 : 5
The full capacity of the petrol tank is unchanged.
Make the totals the same. LCM of 20 and 5 is 20.
Volume of petrol in the end
= 7 u + 20 - 2
= 7 u + 18
16 u = 7 u + 18
16 u - 7 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