Answer:
Av = 12.9 [km/h]
Explanation:
We must remember that the average speed is defined as the relationship between the space traveled over a certain time.
[tex]Av = x/t[/tex]
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
[tex]x_{1}= A_{v}*t\\x_{1}= 15*1.6\\x_{1}=24[km][/tex]
For when Andy was walking
[tex]x_{2}=A_{v}*t\\x_{2}=4.5*0.4\\x_{2}=1.8 [km][/tex]
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.
[tex]x = 24 + 1.8\\x = 25.8 [km][/tex]
The average speed is calculated using the ratio of space to time.
[tex]Av = 25.8/2\\Av = 12.9 [km/h][/tex]
