AFCAT Model Paper 1

GIVEN:
Speed of the boat in still water = 9 km/hour
Distance travelled downstream = 12 km
Total time taken for the round trip = 3 hours
FORMULAE USED:
Upstream speed = Speed of boat – Speed of Stream
Downstream speed = Speed of boat + Speed of stream
Speed = Distance/Time
CALCULATION:
Let the speed of the stream be x km/hr.
Speed of the boat = 9 km/hr
⇒ Speed upstream = (9 – x) km/hr
⇒ Speed downstream = (9 + x) km/hr
Time upstream + Time downstream = 3 hours
Time = Distance/Speed

12

(9–x)

+

12

(9+x)

=3
⇒ x = 3 km/hr
∴ The speed of the stream = 3 km/hr.