Question

In the figure, if DE∥BC, AD = 3cm, BD = 4cm and BC= 14 cm, then DE equals ______.

Options

• 7cm

• 6cm

• 4cm

• 3cm

Answer 1

In the figure, if DE∥BC, AD = 3cm, BD = 4cm and BC= 14 cm, then DE equals 6cm.

Explanation:

Since DE∥BC by the Basic Proportionality Theorem (Thales' Theorem):

So `"DE"/"BC"="AD"/"AB"`

AB = AD + BD = 3 + 4 = 7 cm

`"DE"/14 = 3/7`

`"DE" = 3/7 xx 14 = 6`cm