Question

A 4​-ft vertical post casts a 20​-in shadow at the same time a nearby cell phone tower casts a 120​-ft shadow. How tall is the cell phone​ tower?

Answer 1

change 20 in  to ft

20/12 = 1 2/3 ft

4 ft                               x ft

-------                     =    ---------------

5 /3 ft  shadow           120 ft

using cross products

4 * 120 = 5/3 x

480 = 5/3 x

multiply each side by 3/5

480 * 3/5 = x

288 ft