At Rivera's Laundry, two rectangular soaking tubs are used. The Blue Tub measures 50 cm long by 20 cm wide by 40 cm high, while the White Tub measures 60 cm long by 25 cm wide by 40 cm high. At first, 35 of the Blue Tub's capacity was filled with water, and 12 of the White Tub's capacity was filled with water. Both tubs have a tap at the bottom. The taps were opened at the same time, and water flowed out of each tap at 1 litre per minute.
- Find the volume of water in the Blue Tub at first, in litres.
- How many minutes did it take for the Blue Tub to become empty?
- Find the volume of water remaining in the White Tub when the Blue Tub became empty, in litres.
Need a hint?
Convert each tub's starting volume from cm³ to litres. Then use the Blue Tub's emptying time to find how many litres flowed out of the White Tub.
Worked answer
- Blue Tub capacity = 50 × 20 × 40 = 40,000 cm³.
- Initial water in Blue Tub = 35 × 40,000 = 24,000 cm³ = 24 litres.
- Time taken to empty Blue Tub = 24 ÷ 1 = 24 minutes.
- Initial water in White Tub = 12 × 60 × 25 × 40 = 30,000 cm³ = 30 litres.
- Water remaining in White Tub = 30 − (24 × 1) = 6 litres.
The mistake this question tests
Minutes and hours in rate
Starting with the White Tub's full capacity gives an answer that is too large. Its starting amount must first be found using the fraction that was filled.
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