Question

An athlete plans to row upstream a distance of 6 kilometers and then return to his starting point in a total time of 4 hours. If the rate of the current is 2 km/hr., how fast should he row?

Answer 1

Answer:

He should row at the speed of 12 kilometers per hour.

Step-by-step explanation:

Given:

An athlete plans to row upstream a distance of 6 kilometers and then return to his starting point in a total time of 4 hours.

The rate of current is 2 km/hr.

Now, to find how fast should he row.

Let speed of the athlete row be $x$.

Distance = 6 kilometres.

So, to get the time of upstream:

Rate of upstream = $x-2.$.

Time of upstream = $\frac{x-2}{6}$

Now, to get the time of downstream:

Rate of upstream=$x+2$

Time of downstream = $\frac{x+2}{6}$.

Now, as given total time 4 hours.

Thus, we set an equation:

Time of upstream + time of downstream = total time.

$\frac{x-2}{6} +\frac{x+2}{6} =4.$

$\frac{x-2+x+2}{6} =4.$

$\frac{2x}{6} =4.$

Multiplying both sides by 6 we get:

$2x =24.$

Dividing both sides by 2 we get:

$x =12.$

Therefore, he should row at the speed of 12 kilometers per hour.