Question

vikram wants to spray insecticide on a circular lawn of width 3.5 m built outside his circular plot of land with radius 14 m if an insecticide packet can cover an area of 19.25 m square how many packets of insecticide does he need?

Answer 1

Answer:

Step-by-step explanation:

This is a circle within a circle.

The lawn surrounds the plot.

The radius of the plot is :

Radius = 14 + 3.5 = 17.5M

The area of the plot :

22/7 × 14 × 14 = 616 meters squared.

The area of the outer circle is :

22/7 × 17.5 × 17.5 = 962.5 meters squared.

The area of the lawn :

962.5 - 616 = 346.5 meters square

1 packet = 19.25 meters square

346.5/19.25 = 18

18 packets of insecticide is needed.

Answer 2

Answer: 18 packets

Solution:

Given situation is picturized in attachment.

If we calculate the area of circular park with the help of area of ring formula,than it is easy to compute.

Area of Circular Park
$=\pi \: [{R}^{2} - {r}^{2}] \\ \\ = \frac{22}{7}[ {17.5}^{2} - {14}^{2}] \\ \\ = \frac{22}{7} [306.25 -196] \\ \\ = \frac{22 \times 110.25}{7} \\ \\ = 22 \times 15.75 \\ \\ = 346.5 \: {m}^{2}$
One packet of insecticide covers 19.25 sq-m area,so 346.5 sq-m area covered by

$= \frac{346.5}{19.25} \\ \\ = 18 \: packets$
So,total 18 packets are required.

Hope it works for you.