Question

Class : IX

Subject : Mathematics Assignment 7: Area of Triangles
Formula)
1. The sides of a triangle are 8cm, 15cm and 17cm, find its perimeter and its area. Also find the lengt
altitude drawn on the side with length 17cm.

Answer 1

Explanation:

a=8cm

b=15cm

c=17cm

s=a+b+c/2

=8+15+17/2

=40/2

=20

Using heron's formula,

ar. of triangle= √s(s-a)(s-b)(s-c)

=√20(20-8)(20-15)(20-17)

=√20×12×5×3

=√2×2×5×2×2×3×5×3

=2×2×3×5

=60cm²

On side 17cm,

Ar. of triangle=1/2×b×h

60=1/2×17×h

∴h=60×2/17

=7.05 cm