(A) 42 Km/hr
(B) 84 Km/hr
(C) 90 Km/hr
(D) 100 Km/hr
Correct Option is: B
Smith needs to cover 84 km in 40 minutes
Given that he covers one-half of the distance in one-fourth of the total time
⇒ he covers half of 84 km in one-fourth of 40 minutes
⇒ He covers 42 km in ¼ * 40 minutes
⇒ He covers 42 km in 10 minutes
Now he needs to cover the remaining 42 km in remaining 30minutes
Distance =42 km
Time =30minutes =1/2 hr
Required Speed = Distance / Time
=42/(1/2)=84 km/hr