Let’s look at the options one by one.
Option A:
Total number of wooden logs =4
Number of pieces one wooden log is cut into =3
Number of pieces obtained when four wooden logs are cut into 3 pieces each = total number of wooden logs × number of pieces one wooden log is cut into =4×3
Since we are using the multiplication math expression and not the fraction ÷ whole math expression, this option is incorrect.
Option B:
Total amount of flour used =13 kg
Number of cupcakes made =5
Amount of flour used for each cupcake = total amount of flour ÷ number of cupcakes made=13÷5
Option B is correct since we use the math expression fraction ÷ whole
Option C:
Length of the rope =2 m
Length of each piece =16m
Number of pieces = Length of the rope ÷ length of each piece 2÷16
Since we are using the math expression whole ÷ fraction and not the fraction ÷ whole math expression, this option is incorrect.