The mathematical evidence is that

Let the area of a be m and the area of b be n.

Then m: n = 3/1:4/1.5 = 9: 8.

The total area is 100x200 = 20000m2.

So M+N=20000 square meters.

Known M= 10588 square meters.

N = 9412m2

As for how to divide it, there are two schemes.

Anyway, it can meet the requirement of 3: 4 of the total output of crops A and B.

One: A is long105.88m and wide100m.

B has a length of 94.12m and a width of100m.

Two: A is 200 meters long and 52.94 meters wide.

B is 200 meters long and 47.06 meters wide.

Let the armour area be 3m, the unit output n and the total output 3mn,

Then the total output of B is 4mn, and the output per unit area is1.5n.

Then the area of B: 4mn/ 1.5n=8m/3.

Namely: 3m+8m/3=200* 100.

Area a: 3m =180000/17 =10588m2.

Area B: 20000-10588 = 9412m2.

That is, A accounts for 10588/20000=52.94% of the total.

Take the side length of 200*0.5294= 105.88 and divide it into two rectangles.