Question

The volume of a right circular cylinder is 448pie cm cubic and height is 7 cm find the lateral suraface area and total surface area

Answer 1

The length, breadth and height of a room are 5 m, 4 m and 3 m respectively. Find the cost of white washing the walls of the room and the ceiling at the rate of र 7.50 per m2.

Answer 2

Dimensions of the cylinder :
i ) Volume = v = 448/ pi cm^3------( 1 )
Height of the cylinder = 7 cm
Let radius = r cm
____________________________
Volume of thecylinder = pi × r^2 × h----( 2 )_____________________________
Put the values in ( 2 )
pi × r^2 × h = 448 / pi
pi × r^2 × 7 = 448/ pi
r^2 = ( 448 ) / ( pi × pi × 7 )
r^2 = 64 / ( pi × pi )
Therefore ,
r^2 = ( 8 / pi )^2
r = 8/ pi cm
ii ) Lateral Surface Area ( LSA )
= 2 × pi × r × h
= 2 × pi × 8/ pi × 7
= 2 × 8 × 7
= 112 cm^2
iii) Total surface area ( TSA )
= 2 × pi × r ( r + h )
= 2 × pi × 8/ pi ( 8/ pi + 7 )
= 2 × 8 [ ( 8 × 7)/ 22 + 7 ]
= 16 ( 28 / 11 + 7 )
= 16 ( 28 + 77 )/ 11
= ( 16 × 105 )/ 11
= 1680/11
= 152. 72 cm^2