Hello, sheva2291!

A boat leaves a dock at 3:00 PM and travels due south at 20 km/hr.

Another boat has been heading due east at 15 km/h and reaches the same dock at 4:00 PM.

How many minutes after 3:00 PM were the two boats closest together? Code:

: - - - 15 - - - - :
P 15t B 15-15t D
o-------o-----------o
* |
* |
x * | 20t
* |
* |
o A

Ship starts at dock and sails south at 20 km/hr,

In hours, it has sailed km to point .

Ship starts at (15 km west of ) and sails east at 15 km/hr.

In hours, it has sailed km to point .

. . Hence: .

Let

In right triangle

. . Hence, we have: .

And *that* is the function we must minimize.

I believe the answer is: .