Question

the length of the rectangle is tiwce it's breadth .What is the length , if the perimeter is 90 cm​

Answer 1

$\color{skyblue}{\bigstar \large\underline{\boxed{\bf\pink{Question:-}}}}$

$\sf \red{The \: length \: of \: the \: rectangle \: is \: tiwce \: it's \: breadth } . \\ \sf \red{What \: is \: the \: length , if \: the \: perimeter \: is \: 90 \: cm}$

$\color{skyblue}{\bigstar \large\underline{\boxed{\bf\pink{Answer:-}}}}$

• Perimeter of rectangle = 90 cm
• Let the breadth of rectangle = x
• Then length of Rectangle = 2x

$\sf \blue{Perimeter _ {(Rectangle)} \: =2( \ell + b) }$

$\sf \red{\leadsto \:90= 2(2x + x)}$

$\sf \green{\leadsto \:90= 2(3x)}$

$\sf \orange{\leadsto \: 90=6x}$

$\sf \purple{\leadsto \: x=90 \div 6 \:}$

$\sf \color{violet} \: \leadsto \: x=15 \: cm$

Breadth (x) = 15 cm

$\sf \pink{ \leadsto \: Length(2x) = 2 \times 15 \: = 30 \: cm \: }$

$\color{skyblue}{ \underline{ \boxed{ \bf{Breadth = 15 cm }}}} \\ \color{skyblue}{ \underline{ \boxed{ \bf{Length = 30 cm}}}}$

Answer 2

Answer:

let the length be l and breadth be b.

then, l= 2b

l- 2b= 0 1.

now, 2(l+b)=90

l+b=45 2.

on subtracting 2 from 1 , we get

-3b=-45

b = 15

put b= 15 in 2, we get

l=45-15

=30