Question
A man can row 10 km/h in still water. When the river is
running at a speed of 4.5 km/h, then it takes him 2 h to row to a place and comes back to the initial point . How far is the place (in km) (rounded off to two decimal places)?Solution
Upstream speed = (10 - 4.5) km/h ⇒ 5.5 km/h Downstream speed = (10 + 4.5) km/h ⇒ 14.5 km/h Let the distance of the place be x km. According to the question, (x/5.5) + (x/14.5) = 2 ⇒ (20x × 10 × 10)/(55 × 145) = 2 ⇒ x = (2 × 55 × 145)/(20 × 10 × 10) ⇒ x = 7.975 ∴ The distance of the place will be 7.98 km.
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