A corner shop sells rice in bags. The cost of a bag of rice is directly proportional to its mass. A bag with a mass of 2.4 kg costs £4.32. Work out the cost...
Question 1 Report
A corner shop sells rice in bags. The cost of a bag of rice is directly proportional to its mass. A bag with a mass of 2.4 kg costs £4.32.
- Work out the cost of 1 kg of rice. (1)
- Work out the cost of a bag with a mass of 3.5 kg. (1)
Answer Details
Because the cost of the rice is directly proportional to its mass, the price per kilogram is a fixed rate found by dividing the given cost by the given mass; that rate then applies to any other mass.
(a) The cost per kilogram is \(4.32 \div 2.4 = £1.80\). [1 mark]
(b) Multiplying the rate by the new mass: \(1.80 \times 3.5 = £6.30\). [1 mark]
This is the same "find the rate, then scale" method used throughout direct proportion problems: once £1.80 per kg is established, it applies to a bag of any size.
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