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प्रश्न
Choose the most appropriate option.
A boat travels upstream from A to B and back from B to A in 5 hours. The speed of the boat in still water is 8 km/hour and the speed of the current is 4 km/hour. Then, the distance from A to B is:
विकल्प
9 kms.
10 kms.
15 kms
12 kms
उत्तर
15 kms
Explanation:
Speed of the boat in still water = 8 km/hr
Speed of the current = 4 km/hr
∴ Speed downstream = 8 + 4 = 12 km/hr
Speed upstream = 8 − 4 = 4 km/hr
Let the distance between A and B be x.
Then,
`"x"/12+"x"/4=4` `("x"+3"x")/12=5`
`∴(4"x")/12=5`
`∴"x"=(12xx5)/4=15` km
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