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Did my maths B exam the other day but was absolutely stumped by one question. Spent half an hour thinking about it only to give up.

Question:

A man on a kayak (

*K*) is 3 kilometres out to sea from the nearest point, (

*O*) of a straight beach. His destination (

*D*) is 6 kilometres along the beach from

*O*. The fastest he can paddle is 4 km/hr and his maximum walking speed is 5km/h. How far from

*O*should he go ashore to reach his destination in the least possible time?

Anyways the question was alongside a whole heap of differential problems so I assume you would need to differentiate an equation, find the min SP and that should tell you the distance but I have no idea how to get to the equation or if I was even on the right track.

This was the only question I couldn't answer and it is driving me nuts.

Thanks,

Perjac