Question

Mr Li travelled at an average speed of

56 km/h for 2/1/2hours. In the first hour,
2
his average speed was 50 km/h.
Calculate his average speed for the next
1/1/2 hours

Answer 1

56 km/h

Explanation:

The average speed for Mr. Li's trip will be the total distance divided by the total time for the entire trip.

We are given information about the first half and also the total trip.

First Half:

1 hour at 60 km/h

Full Trip:

56 km/h for 2 1/2 hours

The whole trip had a distance of (56 km/h)*(2.5 h) = 140 km

For the first half, Mr. Li travelled (50 km/h)*(1 h) = 50 km

This left him with (140km - 50km) = 90 km for the last half of the trip.

The total time for the last half was 1.5 h. (2.5 h - 1 h)

Mr. Lin's speed for the last half was (90 km)/(1.5 h) = 60 km/h.

CHECK:

Half Time(h) Speed(km/h) Distance(km)

1 1 50 50

2 1.5 60 90

Total 2.5 140

Does 140km/2.5 h = 56 km/h?

140km/2.5 h = 56 km/h YES