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Mathematics thinking training in the fourth grade
1. First, it is calculated that the length of a and the width of a are both half of 200m, 100m.

The length is 20 meters more than the width, that is, 60 meters long and 40 meters wide.

The total area of this land is 60 * 40 = 2400 square meters.

Small area: (2400-200)/2= 1 100 square meters.

Large area: 2400-1100 =1300m2.

2. After losing 35 sheep and adding 35 cows, adding 35*2=70 cows;

At this time, there are 3 1 more cattle than sheep. It shows that sheep are 35*2-3 1=39 more than cattle.

Originally, there were: (67 1-39)/2=3 16 cows.

Originally there were 67 1-3 16=355 sheep.

I am a math teacher, that's right! You have to use your own brain in the future. Draw a picture, it's simple! !