Question

A young cousin of yours had come for dinner at your place. He could have only one roti whereas your capacity is four rotis. Assume that the rotis are perfectly circular with radius $4cm$. But your cousin wanted to eat as many rotis as you could eat. So, your mum reduced the radius of his rotis to $\_\_\_\_\_$.

• A. 3 cm
• B. 3.5 cm
• C. 2 cm
• D. 1 cm

Answer 1

The correct option is C

2 cm

Area of a circle is given by $\pi (radius{)}^2$. $\Rightarrow$ One roti's area = $\pi (4{)}^2=16\pi c{m}^2$.

Cousin's capacity is 1 roti = area of 1 roti = $16\pi c{m}^2$.

So area of one roti has to be divided in 4 small rotis i.e. $\left(16\pi /4\right)=4\pi c{m}^2$.
Let the reduced radius of roti be r.
Hence,
$\pi r^2=4\pi$,
$\Rightarrow$$r=2cm$.