HOTS Mathematics Primary 5 Rate

Tap A fills a tank in 10 minutes. Tap B drains the same tank in 15 minutes. If the tank starts empty and BOTH taps are turned on at the same time, how long does it take to fill the tank?

A 25 min
B 30 min
C 5 min
D 12.5 min
Show Worked Solution

Worked Solution

Step 1: Fill rate (tap A) = 1/10 of tank per minute. Step 2: Drain rate (tap B) = 1/15 of tank per minute. Step 3: Net fill rate = 1/10 − 1/15 = 3/30 − 2/30 = 1/30 of tank per minute. Step 4: Time to fill 1 tank at 1/30 per minute = 30 minutes. Answer: 30 min

Correct answer: 30 min

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