11.A train travelling at a speed of 75 mph enters a tunnel 3 1/2 miles long. The train is 1/4 mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges ?
A. 2.5 min B. 3 min
C. 3.2 min D. 3.5 min
Answer:B
Total distance covered = (7/2 + 1/4) miles
= 15 / 4 miles
= (18 x 5 /18) km/hr
Time taken = (15 / 4 x 75) hrs
= 1 /20 hrs
= (1 / 20 x 60)
= 3 min.
