Question

The length of a rectangular wooden board is thrice its width. If the area of the board is 192 $c{m}^2$, find the cost of framing it at the rate of ₹5 per 20 cm.

• A. ₹10
• B. ₹16
• C. ₹20
• D. ₹22

Answer 1

The correct option is B

₹16

Let the width of the board be $x$.

The length of the board $=3x$

Area $=l\times b=x\times 3x=3x^2$

$\Rightarrow 3x^2=192$

$\Rightarrow x^2=64$

$\Rightarrow x=8cm$

$3x=8\times 3=24cms$

Perimeter $=2(l+b)=2(24+8)=2\times 32=64cm$

Cost of framing 20 cm = ₹5

$\Rightarrow$ Cost of framing 1 cm $=\frac{5}{20}$

$\Rightarrow$ Cost of framing 64 cm $=\frac{5}{20}\times 64=₹16$