Question

find the volume of cone its total surface area is 7128 square cm and radius of base is 28 CM

Answer 1

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Primary SchoolMath 15+8 pts


Find the volume of a cone , if it's total surface area is 7128 Sq. cm and radius of base is 28 cm .(pie =22/7
plz answer it's urgent. .....
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Comments (5) Follow Report by Neh111 4 weeks ago
RendemoShitiri
what the company answer is...
RendemoShitiri
is it 36960
neh111
yes
RendemoShitiri
Hope u will understand
Total surface area of Cone= 7128
πr(l+r)=7128
22/7×28(l+28)=7128
88(l+28)=7128
88l + 2464=7128
88l=7128-2464
l=4604/88
length= 53
Now, to fine high {height} 'h'=√l2-r2
√(53)2-(28)2
√2809-784
√2025
height=45
Volume of cone= 1/3πr2h
1/3×22/7×(28)2×45
1/3×22×112×45
22×112×15
36960

Answer 2

surface area=7128 cm^2
using formula of surface area 
22/7*28(28+l)=7128
22*4(22+l)=7128
88(22+l)=7128
(22+l)=7128/88
(22+l)=81
l=81-28
l=53
now to find  height of the cone
l^2=r^2+h^2
or h^2=l^-r^2
          =(53)^2 -(28^2)
          =2809-784
     h^2=2025
or      h=45 cm

 using formula of volume of cone

1/3*22/7*(28*28)*45=1/3*22(4*28)*45
                                =110880/3
                                =36960 cm^3