The petrol tank of Ivan's convertible was 55% empty. He went to the petrol kiosk and topped up 21 ℓ of petrol. When he reached the mosque, the petrol tank was 80% 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 |
9x1 =
9 u |
11x1 =
11 u |
20x1 =
20 u |
| Change 1 |
+ 21 |
- 21 |
|
| Change 2 |
- 7 |
+ 7 |
|
| After |
4x4 =
16 u |
1x4 =
4 u |
5x4 =
20 u |
55% =
55100 =
1120 Empty : Total = 11 : 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
= 9 u + 21 - 7
= 9 u + 14
16 u = 9 u + 14
16 u - 9 u = 14
7 u = 14
1 u = 14 ÷ 7 = 2
Capacity of the petrol tank
= 20 u
= 20 x 2
= 40 ℓ
Answer(s): 40 ℓ
