Question

about 2 metre wide surrounds a circular pond of diameter 40 metre how many cubic centimetre of gravel are required to gravel the path to a depth of 7 ​

Answer 1

Diameter of the pond=40m

Radius of the pond = 40/2m = 20m (r)

Width of the path = 2m

Radius of the path and pond together

= (20+2)m = 22m (R)

Pi=22/7

According to the question,

piR^2=pir^2+area of the path

=>area of the path = pi(R^2-r^2)

={22/7(22^2-20^2)} m^2

={22/7(22+20)(22-20)} m^2

=(22/7 × 42 × 2) m^2

=1848/7 m^2

Depth or height of the path = 7m

Thus, amount of gravel required for its construction = area of path×height

=(1848/7 ×7) m^3

=1847m^3

=(1848×1000000)cm^3

=1848000000 cm^3

=1.848×10^9 cm^3

Pls mark my ans as the brainliest

Answer 2

$\sf\red{\underline{\underline{Answer:}}}$

$\sf{1848\times10^{6} \ cm^{3} \ of \ gravel \ is \ required}$

$\sf{to \ grave \ path \ of \ 7 \ m \ depth.}$

$\sf\orange{Given:}$

$\sf{\implies{Radius(r) \ of \ circular \ pond=20 \ m}}$

$\sf{\implies{Circular \ Path \ is \ 2 \ m \ wide}}$

$\sf\pink{To \ find:}$

$\sf{How \ much \ grave \ is \ required \ to \ gravel }$

$\sf{the \ path \ of \ 7 \ m}$

$\sf\green{\underline{\underline{Solution:}}}$

$\sf{Radius(r2) \ of \ pond \ with \ path=20+2=22 \ m}$

$\sf{Area \ of \ path}$

$\sf{= Area \ of \ pond \ with \ path \ - \ Area \ of \ pond}$

$\sf{=\pi\times \ r1^{2} \ - \ \pi\times \ r2^{2}}$

$\sf{=\pi(22^{2}-20^{2})}$

$\sf{=\frac{22}{7}\times(484-400)}$

$\sf{=\frac{22}{7}\times84}$

$\sf{=22\times12}$

$\sf{=264 \ cm^{2}}$

$\sf{Volume \ of \ gravel=Area \ of \ path\times \ Depth}$

$\sf{\therefore{Volume \ of \ gravel=264\times7}}$

$\sf{\therefore{Volume \ of \ gravel=1848 \ m^{3}}}$

$\sf{1 \ m^{3}=1000000 \ cm^{3}}$

$\sf{\therefore{Volume \ of \ gravel=1848\times1000000 \ cm^{3}}}$

$\sf{\therefore{Volume \ of \ gravel=1848\times10^{6} \ cm^{3}}}$

$\sf\purple{\tt{\therefore{1848\times10^{6} \ cm^{3} \ of \ gravel \ is \ required}}}$

$\sf\purple{\tt{to \ grave \ path \ of \ 7 \ m \ depth.}}$