15. A rectangular tank measuring 3 m by 3 m by 1.5 m was 1/3 filled with water. A tap was turned on to fill up with water at a rate of 18 l/min. Every 2 minutes after the tap was turned on, 6 l of water was poured from a pail into the tank. How long did it take for the rectangular tank to be completely filled with water? Leave your answer as a mixed number in its simplest form. [4 marks]
Answer given: 428 2/3 min
Answer given: 428 2/3 min
2/3 x 300 x 300 x150 =9 000 000 cm3 = 9 000 litres
18 x 2 6 36 6
|---------|-----|----------|------|-----
2 min 0 2 min 0
2 min 0 2 min 0
1 cycle (2 min) à 18 x 2 + 6 =
9 000 litres à 9000/42 x 2 ≈ 214 cycles
9 000 - 214 x 42 =
12/18 = 2/3 min
214 x 2 = 428 = min
428 + 2/3 = 428 2/3 min
It was 428 2/3 min.
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