Answer:
Length of the blue whale estimation: 108 ft
Explanation:
Assuming that each scuba diver is 6 ft long, then the length of the blue whale is: 18 x 6 ft
This multiplication can be done using compensation as follows:
first, substitute 18 by 20: 20 x 6 = 120
then, adjust subtracting 6 groups of 2, or 12: 120 - 12 = 108