请你看这道关于万有引力的题：
If the distance between two masses is increased by a factor of 5,the gravitational force of attraction between them will
a.increase by a factor of 5
b.remain Same
c.reduce by a factor of 25
d.reduce by a factor of 5
重点：两物体间距离增加5倍,问万有引力如何变
根据 G正比于 m1*m2/r^2
所以选c
减少为原来的25分之一
看见,英文by a factor of ...既可以说增加,也可以说减少.相当汉语说：是原来的..倍,但是汉语很少说：增加到原来的1/6倍.
所以 你的问题reduce by a factor of 3 to 4意思是你后面的答案：减少到1/3到¼
提醒你注意区别：3 to 4 和 3 over 4
3 to 4 ：3和4 之间
3over4 ：3/4
