Question

The shortest route from London to Southampton is 80 miles. A lorry is expected to take 2 hours to travel this route. The lorry actually travels by a different route which increases the distance by 15%, but it still arrives in 2 hours. By how many more mph than the expected speed does the lorry travel?

Answer 1

Explanation:

original 80 miles in 2 hours.

that means 40 miles in 1 hour.

that means the speed would be 40 mph.

actually traveled : 80 + 15% miles.

80 = 100%

100% + 15% = 115% = 100% × 1.15

=>

80×1.15 = 92 miles

the lorry traveled these 92 miles in 2 hours.

that means 46 miles in 1 hour.

that means the speed was 46 mph.

therefore, it was 6 mph faster than expected.