Question

If the length and breadth of a rectangle are doubled, then its perimeter ____.

• A. triples
• B. doubles
• C. becomes half
• D. becomes 4 times

Answer 1

The correct option is B doubles

We know that
Perimeter of a rectangle, $P=2(l+b)$
where $l$ and $b$ are the length and breadth of the rectangle respectively.

Now, the length and breadth are doubled.

The new length and breadth of the rectangle is,
$l^{\prime }=2l;b^{\prime }=2b$

Perimeter of the new rectangle,
$P^{\prime }=2(l^{\prime }+b^{\prime })$
$P^{\prime }=2(2l+2b)=2\times 2(l+b)=2P$

Therefore, the new perimeter is double the original one.