In ΔABC, if AB = 18 cm, AD = 8 cm, AE = 12 cm, and EC = 15 cm, then:
Given : AB=18 cm,AD=8 cm,AE=12 cm and, EC=15 cm
∴DB=AB−AD=18−8=10 cm
Now, ADDB=810 = 45
and AEEC=1215=45
∵ADDB = AEEC
∴DE∥BC (By converse of basic proportionality theorem)
In a ΔABC, D and E are points on the sides AB and AC respectively. For each of the following cases show that DE || BC: (i) AB = 12cm, AD = 8 cm, AE = 12 cm and AC= 18cm. (ii)AB = 5.6cm, AD= 1.4cm, AC = 7.2 cm and AE= 1.8 cm. (iii) AB= 10.8 cm, BD= 4.5cm, AC = 4.8cm and AE =2.8 cm. (iv)AD = 5.7cm, BD = 9.5cm, AE = 3.3cm and EC = 5.5 cm.