A box with 7 identical bags of rice weighs 7.90 kg. After Mei removed 4 bags, the box with the remaining bags weighs 4.10 kg.
- Find the mass of one bag of rice, in kg.
- Find the mass of the empty box, in grams.
Need a hint?
Work out the mass of the 4 bags Mei removed first, then find one bag. Check your final answer is in grams.
Worked answer
- (a) Mass of the 4 bags removed = 7.90 − 4.10 = 3.80 kg.
- (a) Mass of 1 bag = 3.80 ÷ 4 = 0.95 kg.
- (b) Mass of 7 bags = 0.95 × 7 = 6.65 kg.
- (b) Mass of empty box = 7.90 − 6.65 = 1.25 kg.
- (b) 1.25 kg = 1250 g.
Answer: 1250 g
The mistake this question tests
Habit
Left out the units
Pupils often stop at kilograms or subtract the remaining bags' mass from the full box without first finding one bag's mass, which gives the wrong box mass.
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