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Activity Discussion Math CLASS 7TH PERIMETER AND AREA

• # CLASS 7TH PERIMETER AND AREA

Posted by on June 17, 2023 at 4:33 pm

A wire is bent in the form of a rectangle having length twice the breadth. The same wire is bent in the form of a circle. It was found that the area of the circle is greater than that of the rectangle by 104.5cm2. Find the length of the wire.

replied 1 year, 1 month ago 2 Members · 1 Reply
• ### Majida

Member
June 18, 2023 at 11:30 am
0

Let the breadth of the rectangle be “b”.

The length of the rectangle is twice the breadth, so it’s “2b”.

The perimeter of the rectangle is 2x(b+2b) =6b.

The wire bent in the form of a circle also has a circumference of 6b.

Let “r” be the radius of the circle, that is,

2Ï€r=6b, implies, r= 6b/2Ï€

The area of the rectangle is 2bÂ², and the area of the circle is 9bÂ².

So, according to the question, we have,

Area of the circle – Area of the rectangle = 104.5

9bÂ² – 2bÂ² = 104.5

7bÂ² = 104.5

bÂ² = 104.5 / 7

bÂ² = 14.93

b â‰ˆ âˆš14.93 = 3.86

The total length of the wire used is equal to the perimeter of the rectangle:

Total length of wire = 6b
= 6 Ã— 3.86
= 23.16

Therefore, the length of the wire is approximately 23.16 cm.

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