MixtureshardFree question
5 litres at £4/L are mixed with 7 litres at £10/L. What is the price per litre of the mixture?
A£14.00
B£6.50
C£45.00
D£7.50
E£7.00
Worked solution
Weight each component by its volume: total attribute ÷ total volume. Never average the percentages alone. The correct answer is £7.50. Traps to avoid: £14.00 comes from the "summed prices" error; £6.50 comes from the "swapped weights" error; £45.00 comes from the "wrong divisor" error; £7.00 comes from the "unweighted mean" error.
The wrong answers here have names
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