The perimeter of a rectangle is 25 metres and one of its side is 5 metres. How many metres is the other side.

Given:

Perimeter = 25 metres

Let the two sides of the rectangle be ‘l’ & ‘b’, where l is the length & b is the breadth.

Then, l = 5 m (given)

b = ? (to find)

Now,

Perimeter of rectangle = 2 × (length + breadth)

⇒ 25 = 2 × (l + b)

⇒ 25 = 2 × (5 + b)

Simplifying the bracket, we get,

⇒ 25 = 2 × 5 + 2b

⇒ 25 = 10 + 2b

⇒ 25 –10 = 2b

⇒ 15 = 2b

Or

Perimeter of rectangle = 2 × (length + breadth)

= 25 metres (given)

∴ Perimeter is obtained by multiplying the sum of length and breadth by 2

∴ sum of length can be obtained by dividing the perimeter by 2

∴ sum of length and breadth of the given rectangle = perimeter/2

⇒ 25/2

= 12.5metres

∴ sum of 2 sides is 12.5 metres

Since one side is 5 metres

∴ Other side = 12.5-5 = 7.5 metres