Explanation:

Let the number be 100.

Increase in the number = 40 % = 40 % of 100

= (40/100 × 100) = 40

Therefore, increased number = 100 + 40 = 140

This number is decreased by 40 %

Therefore, decrease in number = 40 % of 140

= (40/100 × 140) = 5600/100 = 56

Therefore, new number = 140 - 56 = 84

Thus, net decreases = 100 - 84 = 16

Hence, net percentage decrease = (16/100 × 100) %

= (1600/100) % = 16 %

Hence, option 4 is the correct answer.