Question

. The difference between the semi perimeter and the sides of ∆ABC are 8 cm, 7 cm and

5 cm respectively. Find its semi perimeter.

Answer 1

21

Explanation:

I'll represent semi perimeter as s

What we know:

s-A=8

s-B=7

s-C=6

A+B+C=2s

we can substitute all the sides in the equation

s-A=8

s-8-A=0

s-8=A

Do this for B and C

A+B+C=2s

(s-8)+(s-7)+(s-6)=2s

3s-21=2s

-21=-s

s=21