Question

Andy took a bus and then walked from his home to downtown. For the

first 1.6 hour, the bus drove at an average speed of 15 km/h. For the
next 0.4 hours, he walked at an average speed of 4.5 km/h. What was
the average speed for the whole journey?

Answer 1

Av = 12.9 [km/h]

Step-by-step explanation:

We must remember that the average speed is defined as the relationship between the space traveled over a certain time.

`Av = x/t`

where:

Av = average speed [km/h]

x = distance [km]

t = time [hr]

For when he was on the bus

The distance can be calculated by clearing the equation, for the term of the distance

`x_(1)= A_(v)*t\\x_(1)= 15*1.6\\x_(1)=24[km]`

For when Andy was walking

`x_(2)=A_(v)*t\\x_(2)=4.5*0.4\\x_(2)=1.8 [km]`

Now the total time is the sum of 1.6 + 0.4 = 2 [hr], and the total distance is the sum of the distances calculated above.

`x = 24 + 1.8\\x = 25.8 [km]`

The average speed is calculated using the ratio of space to time.

`Av = 25.8/2\\Av = 12.9 [km/h]`