In the given figure, DE || BC. If AD = 6 cm, AB = 24 cm and DE = 5 cm, then BC = ____ cm.
20
Consider △ADE and △ABC,
Given, DE || BC
∠ ADE = ∠ ABC
∠ AED =∠ ACB
(Since corresponding angles are equal)
∴△ ADE∼△ ABC (by AA similarity criterion)
⇒DEBC=ADAB
(corresponding sides of similar triangles are in same ratio)
⇒BC=DE×ABAD
⇒BC=5×246
⇒BC=20 cm