RGS Prelim 1997 P2 Q1 (simple percentage question)
(a) An alloy of tin and aluminium contains 52% of tin by weight. Calculate the weight of tin which must be mixed with 84 kg of aluminium to produce a quantity of alloy.
(b) A shopkeeper bought a chest containing 50 kg of tea for $400. He sold this tea in packets, each containing 500 g, for $4.40 per packet.
(i) Find how many packets of tea he sold.
(ii) Find his total profit.
(iii) Express this total profit as a percentage of the total cost price.
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Answer:
(a) By weight, 100% - 52% = 48% of alloy is aluminium is by weight.
84 kg / 48% * 52% = 91 kg
Hence, the weight of tin to be mixed with 84 kg of aluminium is 91 kg.
(b)
(i) Total number of packets = 50kg / 500g
= 50 000 g / 500 g
= 100 packets
(ii) Total profit = $4.40 * 100 - $400 = $40
(iii) $40 / $400 * 100% = 10%
Total profit is 10% of total cost price.
