Analysis: "The number of chickens is one quarter less than that of ducks". For ducks, the unit is 1, and for chickens, the unit is 1- 1/4 = 3/4. "There are many chickens in Abby Mallard ()" At this time, 3/4 of the chickens are in the unit of 1, and the formula is: (1-3/4)÷3/4= 1/3.
If there are only two-fifths more chickens than ducks, there are even fewer chickens (two-sevenths) in Abby Mallard.
Analysis: "The number of chickens is two-fifths more than that of ducks". The unit of duck is 1, and the unit of chicken is 1+2/5 = 7/5. "There are fewer chickens in Abby Mallard ()" At this time, 7/5 of the chickens are in the unit of 1, and the formula is: (7/5- 1)÷7/5=2/7.