A lamp shade like that of fig 15.26 has a height of 12 cm and upper and lower diameters of 10 cm and 20 cm

A.what area material is required to cover the curve surface of the frustum
B.what is the volume of the frustum?
( Give both answers in terms of pie)

A) with lettering by similar triangles= x/5=12/5.

Cross multiply
x=12.
Pythagoream theorem equation: where s is slant height.
s^2=(R-r)^2+h^2
s^2=(10-5)^2 + 12^2
s^2=5^2+12^2
s^2=25+144
s^2=169
Squareroot bothside
s=13.
Surface area of frustum=
Pie*10*26-pie*5*13
=Pie260 - pie65
=pie(260-65)
=pie195 cm^2.

B) volume=1/3*pie*h(R^2+R*r+r^2)
1/3 pie 12(10^2+10*5+5^2)
1/3 * pie *12*175
2100pie/3
=700piecm^3

How do you get it

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(a) 195πcm (b) 700πcm

http://cdn-6.analyzemath.com/Geometry_calculators/frustrum_1.gif

How do you get it

How did you get it

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