Question

Calculate the radius of the circumcircle of a triangle, whose sides are given as $3,4$ and $5$ cm respectively.

• A. $2.1$ cm
• B. $2.2$ cm
• C. $2.3$ cm
• D. $2.5$ cm

Answer 1

Answer: (D)

$2.5$ cm

Circumcircle of a triangle, radius $=$ $\frac{abc}{4\times \sqrt{s(s-a)(s-b)(s-c)}}$
Where, $s=$ $\frac{a+b+c}{2}$
$s=$ $\frac{3+4+5}{2}$
$s=6$

radius $=$ $\frac{3\times 4\times 5}{4\times \sqrt{6(6-3)(6-4)(6-5)}}$

$=$ $\frac{60}{4\times \sqrt{6\left(3\right)\left(2\right)\left(1\right)}}$

$=$ $\frac{60}{4\times 6}$

$=2.5$ cm

Radius of the circumcircle $=2.5$ cm