Question

The perimeter of a triangle is $36cm$ and its sides are in the ratio $a:b:c=3:4:5$, then $a,b,c$ are respectively:

• A. $9cm,15cm,12cm$
• B. $15cm,12cm,9cm$
• C. $12cm,9cm,15cm$
• D. $9cm,12cm,15cm$

Answer 1

The correct option is D $9cm,12cm,15cm$

According to the question,

$a:b:c=3:4:5$

Let $a=3x,b=4x,c=5x$

Perimeter of triangle $=$ Sum of all its sides

$\therefore 3x+4x+5x=36$

$=>12x=36$

$=>x=\frac{36}{12}=3$

Hence, $a=3\times 3=9cm$, $b=4\times 3=12cm$, $c=5\times 3=15cm$