1. A boat running downstream covers a distance of 12km in 3 hours while covering the same distance upstream, it takes 6 hours. What’s the speed of the boat in the still water?
Solution:
Rate of the downstream = 12/3 = 4 km/hr
Rate of the upstream = 12/6 = 2 km/hr
Speed in the still water = 1/2(4+2) = 3 km/hr.
2. A man goes 1 km against the current of the stream in 1 hour and goes 1 km along the current in 20 minutes. How long will it take to go 8 km in stationary water?
Solution:
Rate of the downstream = 1/20*[60] = 3 km/hr.
Note: Speed = Distance/ Time and 60 is multiplied for converting minutes to hours
Rate of the upstream = 1 km/hr.
Speed in still water = 1/2(3+1) = 2 km/hr.
Time taken for 8 km = 8/2 = 4 hours.
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