Question:
In ∆ABC, DE ∥ BC so that AD = 2.4 cm, AE = 3.2 cm and EC = 4.8 cm. Then, AB = ?
(a) 3.6 cm
(b) 6 cm
(c) 6.4 cm
(d) 7.2 cm
Solution:
(b) 6 cm
It is given that DE
Applying basic proportionality theorem, we have:
$\frac{A D}{B D}=\frac{A E}{E C}$
$\Rightarrow \frac{2.4}{B D}=\frac{3.2}{4.8}$
$\Rightarrow B D=\frac{2.4 \times 4.8}{3.2}=3.6 \mathrm{~cm}$
Therefore, AB = AD + BD = 2.4 + 3.6 = 6 cm