In a ΔABC,D,E and F are respectively, the mid-points of BC, CA and AB. If the lengths of side AB, BC and CA are 7cm, 8cm and 9 cm, respectively, find the perimeter of ΔDEF.
In ΔABC,D,E and F are the mid -points of sides, BC, CA , AB respectively
AB = 7cm, BC = 8cm and CA = 9cm
∵ D and E are the mid points of BC and CA
∴ DE || AB and DE = 12AB=12×7=3.5cm
∴ Perimeter of ΔDEF,
=3.5 + 4+4.5 = 12 cm