Question

Calculate the average speed (in km/h) of Charlie, who runs to the store 4 kilometers away in 30 minutes.

Answer 1

8 km/h

Step-by-step explanation:

1st Way

Step 1 - Create a proportion:

60 mins = 1 hr

4 km/30 mins = x km/60 mins

Step 2 - Solve for x by cross multiplying:

4/30 = x/60

240 = 30x

x = 8

4 km/30 mins = 8 km/ 60 mins

8 km/60 mins = 8 km/1h = 8 km/h

Answer: 8 km/h

2nd Way

Step 1 - Make the 30 minutes into 60 minutes by multiplication to get the hour:

30 mins *2 = 60 mins = 1 hr

Step 2 - Multiply the same number with the number of kilometers, 4 :

4 km * 2 = 8 km

This means that he ran 8 km in 1 hr, so that is 8 km/h.

8 km/h