Nick is going to drive 450 miles.
First, solve for Car A:
Car A can go 10.3 miles per litre of petrol. Divide:
450/10.3 = ~43.69 litres in all
Now multiply the number gotten with the cost of Petrol (£1.39)
43.69 x 1.39 = ~£60.72 in all
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Next, solve for Car B:
Car B can go 14.6 miles per litre of diesel. Divide:
450/14.6 = ~30.82 litre in all
Now multiply the number gotten with the cost of diesel (£1.47)
30.82 x 1.47 = ~£45.31 in all
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Car B is cheaper by £15.41, and should be the one used
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hope this helps