Lesson 2.

   Speed - measuring units:

When a car is driven at the average speed of  90 ^km/_hour it means that the car will go a distance of 90 kilometers in one hour. 

The measuring unit can be changed from ^km/_hour  to ^meter/_second

distance = speed × time and time = distance ÷ speed

Example:

If a car is driven at the average speed of 100 ^km/_hour for 4 hours, how far will it go? 

distance = speed × time 

distance =

Example:

How long will it take for a car to go 272 km if it is driven at the average speed of 80 ^km/_hour ?  

time = distance ÷ speed  =

 Instead of using decimals, it is more common to use hours and minutes. The answer (3.4 hours) can be changed to hours and minutes in this way:

Calculate: 0.4×60min = 24 min.

or

It took the car 3 hours and 24 minutes to cover the distance.

Example

A car was driven 161 km in 2 hours and 18 minutes.  What was the average speed for the trip?

speed = distance/time

Then

Try Quiz 2 in Time - speed - distance.