Points A, B, C, and D, in that order, lie on a line. If~$AB = 3 cm$~, ~$AC = 4 cm$~, and~$BD = 6 cm$~, what is CD, in centimeters?

1

2

3

4

5

##### 考题讲解

AB=3 AC=4 则BC=AC-AB=1，BD=6 则 CD=BD-BC=5