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  1. A boat moves downstream at the rate of 1 km in 7
    1
    minutes and upstream at the
    2
    rate of 5 km an hour. What is the speed of the boat in the still water?
    1. 3
      1
      km/hour
      2
    2. 6
      1
      km/hour
      2
    3. 4 km/hour
    4. 8 km/hour
Correct Option: B

Rate downstream of boat =
1
kmph
15
2 × 60

Rate downstream of boat =
2 × 60
= 8 kmph
15

Rate upstream of boat = 5 kmph
∴ Speed of boat in still water =
1
(Rate downstream + Rate upstream)
2

Speed of boat in still water =
1
(8 + 5) =
13
kmph
22

Speed of boat in still water = 6
1
kmph
2

We can find the required answer with the help of given formula :
Here, p =
1km
15
min
2

p =
2 × 60
= 8 kmph
15

q = 5 km/hr
Speed of Boat =
1
(p + q)
2

Speed of Boat =
1
(8 + 5)
2

Speed of Boat = 6
1
km/hr
2



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