A boat is rowed downstream at 15.5km/hr and upstream at 8.5 km/hr. The speed of the stream is________?

A. 3.5km/hr
B. 5.75km/hr
C. 6.5km/hr
D. 7km/hr
Explanation:
Speed Downstream = 15.5 km/hr,
speed upstream = 8.5 km/hr
Speed of the stream = ½ (15.5 – 8.5)km = 3.5 km/hr