Mathematics Mcqs

A steamer goes downstream from one port to another in 4 hours, it covers the same distance upstream in 5 hours. If the speed of the stream is 2km/hr,the distance between the two parts is_______?

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A steamer goes downstream from one port to another in 4 hours, it covers the same distance upstream in 5 hours. If the speed of the stream is 2km/hr,the distance between the two parts is_______?

A. 50km
B. 60km
C. 70km
D. 80 km
Explanation:
Let the distance between the two parts be x km.
Then speed downstream = x/4 km/hr.
Speed Upstream = x/5 km/hr
Speed of the stream = ½ (x/4 –x/5)
Therefore, ½(x/4 –x/5) = 2. => x/4 –x/5 = 4 => x = 80.
Hence, the distance between the two ports is 80km.

The speed of a motor boat is that of the current of water as 36:5. The boat goes along with the current in 5 hours 10 min, it will come back in_______?

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The speed of a motor boat is that of the current of water as 36:5. The boat goes along with the current in 5 hours 10 min, it will come back in_______?

A. 5 hours 50 min
B. 6 hours
C. 6 hours 50 min
D. 12 hours 10 min
Explanation:
Let the speed of motor boat be 36x km/hr and that of current of water be 5x km/hr
Speed downstream = (36x +5x)km/hr = 41x km/hr
Speed upstream = (36 -5x)km/hr = 31x km/hr
Distance covered downstream = (41x × 31/6)km
Distance upstream = [1271x/6 × 1/31x]hrs
= 41/6 hrs = 6hrs 50 min

A boat covers a distance of 30 km in 2 ½ hours running downstream while returning it covers the same distance in 3 ¾ hours. What is the speed of the boat in still water?

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A boat covers a distance of 30 km in 2 ½ hours running downstream while returning it covers the same distance in 3 ¾ hours. What is the speed of the boat in still water?

A. 8km/hr
B. 12km/hr
C. 14 km/hr
D. 15 km/hr
E. None of these
Explanation:
Speed downstream = (30 x 2/5)km/hr = 12km/hr
Speed upstream = (30 x 4/15) km/hr = 8 km/hr
Speed of boat in still water = ½ (12 + 8)km/hr = 10 km/hr