A boat goes $60 k m$ upstream and downs stream in $6 h r$ and $2 h r$ respectively. Determine the product of speed of the stream and that of the boat in still water.

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Solution

x = speed of bolt in upstream $= \frac{60}{6} = 10 k m / h r$
y = speed of bolt in downstream $= \frac{60}{2} = 30 k m / h r$
Product of speed of boat in still water of the stream
$= \frac{x + y}{2} \times \frac{x - y}{2} = \frac{x^{2} - y^{2}}{4} = \frac{900 - 100}{4} = 200$
So, Ans is 200

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A boat goes 60km upstream and downs stream in 6hr and 2 hr respectively. Determine the product of speed of the stream and that of the boat in still water.

x = speed of bolt in upstream =606=10km/hry = speed of bolt in downstream =602=30km/hrProduct of speed of boat in still water of the stream=x+y2×x−y2=x2−y24=900−1004=200So, Ans is 200

A boat goes $60 k m$ upstream and downs stream in $6 h r$ and $2 h r$ respectively. Determine the product of speed of the stream and that of the boat in still water.

x = speed of bolt in upstream $= \frac{60}{6} = 10 k m / h r$
y = speed of bolt in downstream $= \frac{60}{2} = 30 k m / h r$
Product of speed of boat in still water of the stream
$= \frac{x + y}{2} \times \frac{x - y}{2} = \frac{x^{2} - y^{2}}{4} = \frac{900 - 100}{4} = 200$
So, Ans is 200