Please help me with this question

Question

A pole that is 2.9m tall casts a shadow that is 1.49m long. At the same time, a nearby building casts a shadow that is 40.75m long. How tall is the building? Round your answer to the nearest meter.

Answer 1

Hi Monique,

This is a proportions problem.

 

If you set it up to have all thing "talls"  on tops and all shadow lengths on bottoms, then the proportion is this:

 

pole tall                   2.9                 x           building tall

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

shadow length         1.49               40.75       shadow length

 

and so this is the proportion that needs solving.  Cross multiply

 

2.9 * 40.75 = 1.49 * x

 

Divide both sides by 1.49 to isolate "x"

 

(2.9*40.75)/1.49 = x

 

x = 79.312

 

So the building, rounded to the nearest meter, is 79 meters tall.