Hello iz1hpSuppose he lands at a point T, where km. Then, by Pythagoras,

km

So this part of the journey takes ...?... hours.

...?... km

So this part takes ...?... hours.

Add the two times together, to find the total time . Then find the value of that makes a minimum.

(Answer: km from A)

The ends of the tank are squares. Let's suppose they measure meters by meters. And suppose that the tank is meters long. Then we have:2. An open rectangular tank (no top) with square ends is to have a volume of 6400 cubic meters. The base costs $75 per square meter and the sides $25 per square meter. What are the dimensions to build the tank at minimum cost?

Area of base = , at $75 per . So the cost of the base = $...?...

The total area of all four sides is at $25 per . So the cost of the sides = $...?...

So the total cost $C = ...?... (in terms of and )

Now the volume of the tank = area of base x height = .

But this is . So . So ...?... (in terms of ).

Now express in terms of only, and find the value of that will make a minimum.

(Answer: the tank measures 20 x 20 x 16 m.)

Can you complete these now?

Grandad