Question

IN TRIANGLE ABC D E F ARE THE MID POINTS OF AB BC CA.IF AB=6CM BC=7.2CM CA=7.8 CM FIND PERIMETER OF ABC

Answer 1

Its perimeter is 21 cm because we are given with all sides of triangle ABC.
The perimeter of triangle DEF is 10.5 cm

Answer 2

Solution:

It is given that , In Δ AB C , D, E and F are mid points of AB, BC and CA respectively.

Also, AB=6 cm, BC= 7.2 cm, and CA= 7.8 cm

Keep in mind :

Line segment joining the mid point of two sides of triangle is parallel to third side and is half of it.

So, DE ║AC,and DE= $\frac{AC}{2}$

EF║AB, and FE= $\frac{AB}{2}$

DF║BC ,and D F= $\frac{BC}{2}$

DF= $\frac{7.2}{2}=3.6$ cm,

DE=$\frac{7.8}{2}=3.9$ cm,

EF=$\frac{6}{2}=3$ cm,

So, Perimeter of Δ ABC=AB +BC+CA

              =  6  + 7.8 +7.2

               = 21 cm

Perimeter of ΔDEF=DE +E F +D F

           =3 +3.6 +3.9

        = 6.6 +3.9

        = 10.5 cm