Tap P was turned on at 14 10 to fill an empty cubical tank at a rate of 6 litres per minute. Tap P was turned off at 14 19. At 14 19, the tank was 25% filled with water.
- Find the volume of water, in litres, that flowed into the tank from Tap P.
- Find the length of one edge of the tank, in cm.
Need a hint?
Convert litres to cm³ before using the volume formula, and remember 25% means one quarter of the full tank.
Worked answer
- (a) Time taken = 14 19 − 14 10 = 9 minutes.
- (a) Volume of water = 6 × 9 = 54 litres.
- (b) 54 litres = 54 000 cm³, since 1 litre = 1000 cm³.
- (b) 54 000 cm³ is 25% of the tank, so full volume = 54 000 × 4 = 216 000 cm³.
- (b) Edge = 60 cm, since 60 × 60 × 60 = 216 000.
Answer: 60 cm
The mistake this question tests
Habit
Converting units (kg, ℓ, m, cm³)
Many pupils skip the litre-to-cm³ conversion and find the cube root of 216, getting 6 cm instead of 60 cm.
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