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)

15 answers

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

(a) 195πcm (b) 700πcm

How do you get it

How did you get it

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

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