The sun must be very low in the sky, as a 24foot building would cast the 168-foot shadow.
Step-by-step explanation:
Always be careful that the units of your calculation are consistent. It is a common trick in word problems to see if you are attentive.
It is best to stay in feet rather than inches in this problem.
The 36 inches is equal to 3 ft.
I prefer to just use a proportion to solve:
3/21 = x/168 Using cross products we calculate x = 24 ft