### Home > CALC > Chapter 11 > Lesson 11.1.2 > Problem11-26

11-26.

Sketch the situation. Your sketch should have similar right triangles.

If the child's distance from the light is d and their shadow length is s, then:

The equation can be rewritten as 2s = d.
Now differentiate.

Now use the information given in the problem to solve for ds/dt.