# Find the Area of a Triangle, Whose Sides Are : 21 M, 28 M and 35 M - Mathematics

Sum

Find the area of a triangle, whose sides are :

21 m, 28 m, and 35 m

#### Solution

Sides of ∆ are
a = 21 m
b = 28 m
c = 35 m

S = (a + b + c)/2 = (21 + 28 + 35)/2

= 84/2 = 42

area of Δ = sqrt(S(S - a)(S - b)(S - c))

= sqrt(42(42 - 21)(42 - 28)(42 - 35))

= sqrt(42 xx 21 xx 14 xx 7)

= sqrt(7 xx 3 xx 2 xx 3 xx 7 xx 2 xx 7 xx 7)

= sqrt(7 xx 7 xx 7 xx 7 xx 3 xx 3 xx 2 xx 2)

= 7 xx 7 xx 3 xx 2 = 294  "m"^2

Concept: Perimeter of Triangles
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#### APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 20 Area of a Trapezium and a Polygon
Exercise 20 (A) | Q 1.3 | Page 223
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