一个半径长是4毫米的圆形零件,画在一幅比例尺是25:1的图纸上,它的图上半径是多少厘米?
4毫米=0.4厘米,
0.4×251=10(厘米);
答:它的图上半径是10厘米.
口语交际
A:Hi, Mike, 小题1:_______
B: Yes ,Ido. It’s more than 6 billion.
A: Wow, that’s large! 小题2:_______
B: Yes.It will reach about 9 billion by 2050.
A: 小题3:___________
B: It’s going to be bad. 小题4:_____. We won’t have enough food,water,or energy in the future.
A; 小题5:_________
B: Yes, it is.Governments all over the world are working to solve the problem.
A: I hope the population of the world won’t grow so fast.
B: Me ,too.
试述张节理与剪节的差异性。