Suppose you make a model airplane. if you know that the ratio of the length of its wings to the wings of the actual airplane is 1: 100, how can you estimate the length of the real airplane's wing? with this in mind, how might you go about measuring the height of a tall building or a large tree without getting on a ladder and using measuring tape? explain how you might perform an indirect measurement. be creative!

First to find the length of the wing:
model/real = 1/100
m/r = 1/100*r
m = 1/100*r
m*100 = 1/100*100*r
100*m = r, so just multiply the model wing times 100
Next, to find the height of the building or tree:
A shadow makes a right triangle. We assume the ground is level and that the building or tree is vertical.

You have a ruler or yard stick that you know the height of. it casts a shadow when it is heal vertical and sits on the same ground as the building. 

y = height ruler or yard stick 
b = height of building or tree 
ys = length of rulers shadow 
bs = building shadow 

so 
y:ys as b:bs 

36in: 12in as bin:3600in 
from now on using inches 
36:12 as b:3600 

3:1 as b:3600 
3/1 as b/3600 
3/1 * 3600 = b/3600 * 3600 
3/1 * 3600 = b/3600 * 3600 
3/1 * 3600 = b 
10,800 in = b inches (convert inches to feet)
900 ft= building height in feet.
I really hope this helps! :)

Whose mistake? can you give more details to what the question is asking?