Surface area and volume for class 9th by kuldeep Bartwal Deep
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Transcript of Surface area and volume for class 9th by kuldeep Bartwal Deep
DIFFERENT TYPES OF SHAPES
•CUBOID• CUBE
• SPHERE
• HEMISPHERE
• CYLINDER
•CONE
When a plane through the centre of a sphere cuts it into two equal parts is called a
hemisphere.
FORMULAE’S
EXAMPLE -1A hemispherical dome of a building needs to be painted. If the circumference of the base
of the dome 15.8,find the cost of painting it,given the cost of painting Rs. 10per
100cm.square.
SOLUTON-1
2x22/7x79/10x79/102
= 392.30 (cm ) =3920.30=Rs.1,96,150 (Ans)
EXAMPLE-2
The circumference of the edge of a hemispherical bowl is 132cm.Find the capacity of the bowl.
SOLUTION-2 Circumference = 2 r
132 =2x22/7xrR= 132x7/2x22
R=21
Capacity=
2/3x22/7x21x21x213
= 19404 cm (Ans)
EXAMPLE-3
Find the volume ,curved surface area and the total surface area of hemisphere of diameter 7 cm?
SOLUTION -3
) =2 x14x14cm.square =(392 )cm.square =2/3x22/7x7/2x7/2x7/2 cm.cube
2x22/7x2/7/2 =77cm.square
539/6 = 89.83cm.cube
3x22/7x7/2x7/2 =115.5cm.square. (Ans)
• A hemisphrical bowl is made up of steel,0.75m
thick.The inner radius of the bowl is 15m . Find the outer curved surface area ?
• R = thickness + inner radius• = 0.75 + 15 = 15.75
= 2x22/7x15.75x15.75 = 1559.25m.square.
EXAMPLE-5• The volume of hemisphere is 5544cm.square. Find its radius ?
SOLUTION -5
• 3• 5544 = 2/3x22/7x r • 3• 5544x7/2x22= r• cube root of r =756 • r = 19.63cm.cube.
EXAMPLE- 6• If diameter of a solid hemisphere is half then
its total surface area ill be decreased by 75%.
SOLUTION - 6• Let diameter be = x• Radius = x/2
• 3 (x/4) = 3 r.square./16• change in T.S.A original-new/originalx100• 3 r.square / 4 -3 r.square /16 x 100 • 4
• 12 r.square – 3 r.square/16/3 r square/4
• 9 x.square/16/3 r.square/4• 3/4x100• = 3x25• = 75% (Ans)
QUESTION - 1 & 2• Find the volume of hemisphere whose radius
is 21 cm ? • ANS. 19404 cm.cube
Find the total surface area and the curved surface area whose radius is 7 cm?
ANS. 462 cm. square 308 cm .square
THANKYOU