Question

If a car travels 200 km at an average velocity of 40 km/hr, and a second car starting 1.0 hour later arrives at the 200 km destination at the same time, what is the average speed of the second car?

Answer 1

The average speed of the second car is `50 "km"/"h"`

Explanation:

For the first car we have,

Distance: 200 km
Average speed: 40 km/hr
Start Time: Let's say 12:00 pm, noon
Stop Time: `200/40= 5 " hrs"`, which is 5:00 pm

For the second car, we have,

Distance: 200 km (same distance)
Average speed: ? This is what we want to know
Start Time: 1:00 pm
Stop Time: 5:00 pm (same time)

Because `"Distance" = "Rate"xx"Time"`, we have

200 km = `Rxx4 " hrs"` (time between 1:00 pm and 5:00 pm)
`R=(200 " km")/(4 " hrs") = 50 "km"/"h"`