Answer:
4000 is size of a crowd walking in a charity fundraising March.
Step-by-step explanation:
Given:
Dimensions of rectangular space 10 feet by 12000 feet
So we can say that,
Length = 1200 ft
Width = 10 ft
Now we will calculate the area of rectangular space which is given by
Hence Area will be = 
Now we know that 40 people occupy a rectangle measuring 10 feet by 12 feet.
Length = 12 ft
Width = 10 ft
Area = 
It says that 40 people are occupied in 120 
So how many people will be there in 12000 
By using unitary method we get,
Number of people = 
Size of a crowd walking in a charity fundraising March is 4000.