Question

perimeter of a rectangle is 21 cm . and its length is 5 1/2 cm.find its breadth?​

Answer 1

GIVEN :–

• Perimeter of rectangle = 21 cm

• Length of rectangle = 5½ cm = (11/2) cm

TO FIND :–

• Breadth = ?

DIAGRAM :–

$\setlength{\unitlength}{1 mm}\begin{picture}(0,0)\put(32,-2){ \tt{Breadth} }\put(8,-14){ \tt{Length} }\put(-12,10){ \tt{D} }\put(28,10){ \tt{C} }\put(-12,-13){ \tt{A} }\put(28,-13){ \tt{B} }\put(-11.5,8.2){\line(0,-6){17}}\put(30.5,8.2){\line(-4,0){42}}\put(30.5,-8.8){\line(-4,0){42}}\put(30.3,8.1){\line(0,-4){17}}\end{picture}$

SOLUTION :–

• We know that –

$\\ \: \:{\huge{.}} \:\: { \bold{Perimeter \: \: of \: \: rectangle = 2(Length + Breadth)}}$

• Now put the values –

$\\ \implies { \bold{21 = 2 \left( \dfrac{11}{2} + Breadth \right)}}$

$\\ \implies { \bold{21 = 2 \times \dfrac{11}{2} +2( Breadth) }}$

$\\ \implies { \bold{21 = 11+2( Breadth) }}$

$\\ \implies { \bold{21 - 11 =2( Breadth) }}$

$\\ \implies { \bold{2( Breadth) = 10}}$

$\\ \implies { \bold{Breadth = \cancel \dfrac{10}{2}}}$

$\\ \implies \large{ \boxed { \bold{Breadth = 5 \: cm}}}$

Answer 2

Explanation:

${\red{\underline{\underline{\bold{Given:-}}}}}$

• Perimeter of a rectangle = 21cm

• Length of the rectangle = $5 \frac{1}{2}$cm

${\blue{\underline{\underline{\bold{To\:Find:-}}}}}$

• The breadth of the rectangle

${\green{\underline{\underline{\bold{Solution:-}}}}}$

$\tt\pink{Formula\:used:-}$

Perimeter of rectangle = 2(length + breadth)

Let the breadth of the rectangle be 'b'

Given,

Perimeter = 21cm

Length = $5 \frac{1}{2}$cm

$2(5 \frac{1}{2} + b) = 21 \\ \\ \implies\frac{11}{2} + b = \frac{21}{2} \\ \\ \implies b = \frac{21}{2} - \frac{11}{2} \\ \\ \implies b = \frac{21 - 11}{2} \\ \\ \implies b = \frac{10}{2} \\ \\ \implies b = 5$

$\large\purple{{\underline{\boxed{\textbf{Breadth\:of\:rectangle= 5cm}}}}}$