Decreasing size of person's shadow as they walk toward a lamp

[Akash47]

Homework Statement

If a man of height 6ft moves with 5ft/sec velocity towards a lamp hanging at 15ft height, then at what rate his shadow will decrease?

Homework Equations

Not sure but dynamic equations can help.

The Attempt at a Solution

I have no idea about how I can approach.So I want some ideas to reach the solution.

 

[ehild]

Homework Statement

If a man of height 6ft moves with 5ft/sec velocity towards a lamp hanging at 15ft height, then at what rate his shadow will decrease?

Homework Equations

Not sure but dynamic equations can help.

3. The attempt at a
Evolution
I have no idea about how I can approach.So I want some ideas to reach the solution.

A drawing will help. Can you find the length of the shadow (s) in terms of the position of the man (x), and the heights H and h?

 

[.Scott]

Put the lamp at X=0, Y=15.
The position of the man will be X.