Tarun can row a boat upstream for 27 km in 3 hours and downstream for 99 km in 3 hours. If Tarun rows a distance of 42 km in still water and a distance of 66 km downstream, what is the total time taken?
- AOption (a)
6 hours
- BOption (b)
2 hours
- COption (c)
5 hours
- DOption (d)
4 hours
- EOption (e)
3 hours
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Correct answer
4 hours
Why this answer is correct
Given:
Distance travel in 3 hours (Upstream) = 27 km
Distance travel in 3 hours (Downstream) = 99 km
Concept Used:
Upstream Speed = B - S
Downstream Speed = B + S
Time (T) = Distance (D)/Speed(S)
B = Speed of Boat
S = Speed of Stream
Calculation:
According to the question, we get
27/(B - S) = 3
⇒ B - S = 9 km/h ---(i)
99/(B + S) = 3
⇒ B + S = 33 km/h ---(ii)
From (i) and (ii), we get
B = 21 km/h
S = 12 km/h
According to the question, we get
Total Time taken = Time taken in Downstream + Time taken in Still water
⇒ {66/(21 + 12)} + (42/21)
⇒ (66/33) + (42/21)
⇒ (2 + 2) hours
⇒ 4 hours
∴ The total time taken by boat is 4 hours.