Question

How many plants will be there in a circular bed whose outer edge measures $30$ cm allowing $4$ cm${}^2$ for each plant?

• A. $18$
• B. $750$
• C. $24$
• D. $120$

Answer 1

Answer: (A)

$18$

Numbers of plants $=\frac{Areaofbed}{Arearequiredforeachplant}=\frac{\pi r^2}{4}$

Circumference $=30cm\Rightarrow 2\pi r=30\Rightarrow r=\frac{15}{\pi }$

$\therefore$ Number of plant $=\frac{\pi \times {\left(\frac{15}{\pi }\right)}^2}{4}=\frac{\pi \times 15\times 15}{4\times \pi \times \pi }=\frac{225\times 7}{88}=17.89\approx 18$