The Petrol Problem

Question


The petrol tank in Bob's car is 1/8 full. When 30 litres of petrol are added, the tank become 3/4 full. If the petrol costs $1.38 per litre, how much will it cost her to fill the remaining quater of the tank?


A) $8.80
B) $13.80
C) $16.56
D) $24.84
E) $41.40


Answer & Working


1/8 + 30L = 3/4


3/4  - 1/8
6/8  - 1/8 = 5/8
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Let 'x' be the full fuel tank


5/8x = 30
x = 48L (The full fuel tank can hold 48L)


1/4x = 48/4
1/4x = 12L (So a quarter of the tank contains 12L)


(Now we have to find how much 12L costs)
12 * 1.38


C = $16.56 (Remember the units)