Question

If a body travels a distance of d1, with a speed v1

Answer 1

time taken is
t1=d1/v1

Answer 2

Let distance travelled with speed v1 be D1.

Let distance travelled with speed v2 be D2.

Time taken in both cases = t.

So we have :

Average speed = [math]total distance / total time taken[/math] = [math](D1+D2)/2t[/math]

[math]= (v1t+v2t)/2t = (v1+v2)/2.[/math]

But when times are different, we have :

Avg speed = [math]([/math][math]v1t1+v2t2)/(t1+t2)[/math]