area of the base of a cone is 1386 sq cm and its height is 28 cm find radius,slant height,surface area of cone
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Step-by-step explanation:
Area of the base of a cone = 1386sq.cm.
Height,h= 28cm.
Surface are = ??
Therefore by using the formula ,
Area of base of cone = pi*r^2
1386 = 22/7*r^2
1386*7/22 = r^2
63*7 = r^2
441 = r^2
r = 21cm.
We got the radius.
Now we find the slant height,
We know that,
l^2 = r^2 + h^2
l^2= (21)^2 + (28)^2
l^2 = 441 + 784
l^2 = 1225
l = 35cm.
So we got the value of radius and slant height now we can easily find the surface area of cone.
By using the formula,
Surface are of a cone= pi * r*l
= 22/7*21*35
=22*3*5
= 330sq.cm.
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