Question

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

• A. 18
• B. 19
• C. 24
• D. 21

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.
$\Rightarrow$ $2\pi r=30$
$\Rightarrow$ $r=\frac{30}{2\pi }$
$\Rightarrow$ $r=4.77cm$
Area of the circular bed = $\pi r^2$
$\Rightarrow$ Area = $\pi \times {4.77}^2$
$\Rightarrow$ Area = $3.14\times {4.77}^2$
$\Rightarrow$ Area = 71.44 cm${}^2$
Number of plants that can be planted in the circular bed
= $\frac{Areaofthecircularbed}{Areaoccupiedbyeachplant}$
= $\frac{71.44c{m}^2}{4c{m}^2}$
= $17.86\cong 18$
Therefore, the required numbers of plant is 18.