1)
188.4/3.14=60
(60+4)/2=32
3.14*(32²-30²)
=3.14*(1024-900)
=3.14*124
=389.36㎡
2)解设原来边长为X
(X+300)²-X²=630000
X²+600X+90000-X²=630000
600X=540000
X=900
∴X²=900²=810000㎡=81公顷
1)
188.4/3.14=60
(60+4)/2=32
3.14*(32²-30²)
=3.14*(1024-900)
=3.14*124
=389.36㎡
2)解设原来边长为X
(X+300)²-X²=630000
X²+600X+90000-X²=630000
600X=540000
X=900
∴X²=900²=810000㎡=81公顷