Question

Find the area of a triangle with sides 28 cm, 21 cm and 35 cm.​

Answer 1

Answer:

p=a+b+c

p=28+21+35

p=84

s=p/2=84/2=42

Area=√s(s-a)(s-b)(s-c)

=√42(42-28)(42-21)(42-35)

=√42×18×21×7

=2×3×7×3×3×2×3×7×7

=2×2×3×3×3×3×7×7×7

=2×3×3×7×√7

=6×21×√7

=126√7 cm²

Answer 2

Answer:

★ Area = 294 Cm² ★

Step-by-step explanation:

Given:

• Sides of triangle are 28, 21 and 35 cm

To Find:

• Area of the triangle

Solution: Let in ∆ABC,

• AB = 35 cm
• AC = 21 cm
• BC = 28 cm

• To find Area of ∆ABC, We have to use Heron's Formula

★ We know that Semi perimeter = AB+ BC+ CA/2 ★

∴ S = 35+28+21/2 = 84/2 = 42

† Heron's Formula = √S( S – a ) ( S – b)(S– c ) †

$\small\implies{\sf }$ √42 ( 42 – 35) ( 42 – 28 ) ( 42 – 21 )

$\small\implies{\sf }$ √42 x 7 x 14 x 21

$\small\implies{\sf }$ √2 x 3 x 7 x 7 x 2 x 7 x 3 x 7

$\small\implies{\sf }$ 2 x 3 x 7 x 7

$\small\implies{\sf }$ 294 Cm²

Hence, Area of ∆ABC is 294 Cm²