Question 1033632


the question did not say to estimate.
the questions said what is the difference.
you're probably close, but you're certainly not right on.


let's see what the answer would be if we didn't round the intermediate results.


petrol car costs 1.39 per liter and gets 10.3 miles per liter.
diesel car costs 1.47 per liter and gets 14.6 miles per liter.


distance traveled is 450 miles.


cost for petrol car is 450 / 10.3 * 1.39 = 60.72815534 pounds.
cost for diesel car is 450 / 14.6 * 1.47 = 45.30821918 pounds.


the difference is = 15.41993616 which is 15.42 pounds rounded to 2 decimal places.


you said 18 pounds.


i suspect you lost 2 marks because you rounded your numbers up front.


unless you are specifically asked to round your numbers in order to get a rough estimate, you need to use the exact values for the calculations and only round at the end.


your estimate versus the actual difference was about (18/15.42 - 1) * 100 = roughly 17% too high rounded to the nearest percent.