Question

a tree that is 20 feet tall casts a shadow 30 feet long. a girl standing next to the tree has a shadow 9 feet long. how tall is the girl?

Answer 1

The shadow of the three is proportional to the shadow of the girl, then we can use a rule of three:

if x is the height of the girl: 20 is to 30 is the same as x is to 9

This can be written as:

$\frac{20}{30}=\frac{x}{9}\Longrightarrow x=\frac{9\cdot20}{30}=\text{ 6}$

Answer:

The girl is 6 feet tall