A car travels from calabar to Enugu, a distance of P km with an average speed of U km per hour and continues to benin, a distance of Q km, with an average speed of Wkm per hour. Find its average speed from Calabar to Benin

A.
(frac{(p + q)}{pw + qu}) 
B.
(frac{uw(p + q)}{pw + qu}) 
C.
(frac{uw(p + q)}{pw}) 
D.
(frac{uw}{pw + qu})
Correct Answer: Option B
Explanation
Average speed = (frac{text{total Distance}}{text{Total Time})
from Calabar to Enugu in time t_{1}, hence
t_{1} = (frac{P}{U}) also from Enugu to Benin
t_{2} (frac{q}{w})
Av. speed = (frac{p + q}{t_1 + t_2}
= (frac{p + q}{frac{p}{u} + frac{q}{w})
= p + q x (frac{uw}{pw + qu})
= (frac{uw(p + q)}{pw + qu})