Question

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

• A. 18
• B. 750
• C. 24
• D. 120

Answer 1

The correct option is A 18

Given: Outer edge of the circular bed = Circumference = 30 cm.
Circumference = $2\pi r$, where $r$ is the radius of the circular bed.
$\Rightarrow$ $2\pi r=30$
$\Rightarrow$ $r=\frac{30}{2\frac{22}{7}}$
$\Rightarrow$ $r=4.7cm$.
Area of the circular bed = $\pi r^2$
$\Rightarrow$ Area = $\frac{22}{7}\times {4.7}^2$
$\Rightarrow$ Area = 69.42 cm${}^2$.
Number of plants that can be planted in the circular bed = $\frac{Areaofthecircularbed}{Areaoccupiedbyeachplant}$
= $\frac{69.42c{m}^2}{4c{m}^2}$
= $17.3\cong 17$.
Therefore, the required number of plants is 17.