Question

A covers 40km by 60kmph and 60km by 40kmph, find the average speed?

Answer 1

time = distance / speed
t = d / v
t₁ = d₁ / v₁
t₂ = d₂ / v₂
t = t₁ + t₂
d = d₁ + d₂

The average speed:
$<span>v_{av}=\frac{d}{t}=\frac{d_1+d_2}{\frac{d_1}{v_1}+\frac{d_}{v_2}}=\frac{40+40}{\frac{40}{60}+\frac{40}{40}}=\frac{80}{\frac53}=80\times\frac35=48\ kmph$