HOTS Mathematics Primary 5 Rate

A tap fills a tank at 15 litres per minute. After 8 minutes, a second tap is turned on that drains the tank at 6 litres per minute. How many litres are in the tank after another 12 minutes?

A 228 litres
B 180 litres
C 300 litres
D 192 litres
Show Worked Solution

Worked Solution

Step 1: Calculate litres filled in the first 8 minutes (only fill tap on). 15 × 8 = 120 litres Step 2: Find the net rate when both taps are on. Net rate = 15 − 6 = 9 litres per minute Step 3: Calculate litres added in the next 12 minutes. 9 × 12 = 108 litres Step 4: Total in tank. 120 + 108 = 228 litres

Correct answer: 228 litres

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