Question
A man can go on a motorboat with a speed of 18 km/hour
in still water to a certain upstream point and return to the starting point in a river that flows at a speed of 14 km/hour. Find the average speed of the motorboat for the total journey.Solution
Let the speed of the boat be b km/hour and the speed of the current be s km/hour. Average speed = 2xy/ (x+ y) (here, x is the speed of downstream and y is the speed of upstream)  = (2 (b +s) (b-s))/ ((b+ s +b -s)) = (b2 – s2)/b = (324 - 196)/18  = 128/18  = 64/9 Km/h
More Boats and streams Questions
√3598 × √(230 ) ÷ √102= ?
Simplify the following expressions and choose the correct option.
45% of 640 + (2/5 of 350) = ?
√225 + 27 × 10 + ? = 320
32 X 25 ÷ 4 + 12 of 30 = ? X 5 - 30Â
1440 ÷ 12 + 540 ÷ √36 + ? = 180 * 3
4567.89 - 567.89 - 678.89 = ?
- What will come in place of the question mark (?) in the following questions?
18×4+96÷8=? ((12+12+12+12)÷4)/((8+8+8+8+8+8)÷16) = ?
9999² + 1111² =?
- What will come in the place of question mark (?) in the given expression?
(120 - ?) ÷ 2 + 35 = 86 - 11
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