we put a copper wire to wind around the ciecle whose diameter is 30 cm ,just can be wound 12 rings,c

题目

we put a copper wire to wind around the ciecle whose diameter is 30 cm ,just can be wound 12 rings,can you work out the length of the copper?
if the perimeter of a rectangle and a square is equal ,if the length of the square is 3.5dm,the length of rectangle is 5 dm,then how long is the width?(answer in meter)
if the perimeter of a square is7/2m,use 5/8 of its perimeter,what's the rest meter?
the perimeter of a rectangle is 24.8m,the length is 3times than the width,what's the area of a rectangle?
the perimeter of a rectangle is 24cm,draw a square on its every side,the sum of every new square is 208cm²,what's the area of the original rectangle?

答案

1.我们将一根铜线环绕一个直径为30cm的圆圈,可以绕12圈,你能算出铜线的长度吗?
30*12=360cm 答：铜线长度为360cm.
2.如果一个长方形和一个正方形的周长相等,正方形一边为3.5dm,长方形的长为5dm,那么长方形的宽为多少?（用米作答）
3.5*2-5=2dm=0.2m 答：长方形的宽为0.2m.
3.如果一个正方形的周长为7/2m,用掉了其周长的5/8,剩下多少米?
7/2*(1-5/8)=21/16m 答：剩下21/16米.
4.一个长方形的周长为24.8m,其长是宽的3倍,那么这个长方形的面积为多少?
设宽是xm,则长为3xm,(x+3x)*2=24.8 得出：x=3.1 则长是9.3m,宽为3.1m
9.3*3.1=28.83平方米 答：长方形的面积为28.83平方米.
5.一个长方形的周长为24cm,在其每一边都画一个正方形,新正方形的面积和为208平方厘米,那么原长方形的面积为多少?
长方形的长宽和为12cm,设长为x厘米,宽则为12-x厘米.
新正方形有4个,其中两个边长是x厘米,另两个边长为12-x厘米.x的平方+（12-x）的平方=208/2=104
解方程,得出：x=10或2,根据长比宽长的原则,原长方形的长为10厘米,宽为2厘米,则面积为20平方厘米.