A person can row 10 km/h in still water. If it takes him exactly twice as long to row upstream as to row downstream over the same stretch, find the speed of the current.
Explanation:
Let speed of current be c km/h. Downstream speed = 10 + c, Upstream speed = 10 - c. Given: 2 * (10 - c) = 10 + c => 20 - 2c = 10 + c => 3c = 10 => c = 10/3 = 3.33 km/h.
Excluding regular route passenger stops, the speed of an express coach is 64 km/h and including stops it is 48 km/h. For how many minutes does the coach stop per hour?
Explanation:
Since time is inversely proportional to speed when distance is constant, the ratio of time taken is the reciprocal of the speed ratio: 1/4 : 1/7 = 7 : 4.
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