Question

If B is the mid-point of $\overline{AC}$ and C is the mid-point of $\overline{BD}$, where A, B, C, D lie on a straight line, say why AB = CD?

Answer 1

B is the mid-point of $\overline{AC}$.
$\therefore AB=BC$ (i)
And C is the mid-point of $\overline{BD}$
$\therefore BC=CD$ (ii)
From equation (i) and (ii), we get
AB = CD