A person in a rowboat 2 miles from the nearest point P on a straight shoreline wishes to reach a house 6 miles down the shoreline from P.If the person can row at a rate of 3 miles per hour and walk...

A person in a rowboat 2 miles from the nearest point P on a straight shoreline wishes to reach a house 6 miles down the shoreline from P.

If the person can row at a rate of 3 miles per hour and walk at a rate of 5 miles per hour, find the least amount of time required to reach the house.

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neela | High School Teacher | (Level 3) Valedictorian

Posted on

The nearest distance of the person  to the spot P on the shore = 2miles.

Let starting point of the person to row the boat be S. Then SP = 2.

Let the house be at the spot H on the bank of the river.

Then SP = 2, SH = 6 miles.

Therefore PSH form a right angled triangle with right angle at S.

Therefore PS^2+SH^2 = PH^2 by Pyhagoras theorem.

2^2+6^2 = PH^2.

Or PH^2 = 2^2+6^2 = 4+36 = 40

Therefore PH = sqrt(40) = 6.3246 miles.

Therefore the time required to row SH = 6 miles at the rate of 3mph = 6/3 = 2 hours.

The time required to walk the distance of PH = 6.3246 miles at the rate of 5 miles per hour = 6.3246/5 = 1.2649 hours = 1 hour 15.9 minutes nealy.

So the least time to reach is the option of walking.

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