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

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 2*s* = *d*.

Now differentiate.

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