\begin{array} { l } { \text { The outer and inner diameters of a hemis

1.	\begin{array} { l } { \text { The outer and inner diameters of a hemispherical } } \\ { \text { bowl are } 17 \mathrm { cm } \text { and } 15 \mathrm { cm } \text { respectively. Find the } } \\ { \text { ost of polishing it all over at } 25 \text { paisa per cm? } } \\ { \text { (Take } \pi = \frac { 22 } { 7 } ) } \end{array}
Answer» Given,Outer diameter of the hemisphere 2r =17cm r=17/2 Its Inner diameter 2r=15cm r=15/2 [Note:- C.S.A:-Curved Surface Area] Therfore outer C.S.A = 222/717/217/2 =454.142sq cm Its inner C.S.A= 222/715/215/2 =343.571sq cm Then 454.142+343.571=797.7134 Rate of painting it=25 paise=Rs. 0.25 Therefore, 797.7134*0.25=Rs.199.4275 Hence the cost of polishing the hemispherical bowl is Rs. 199.43 .

\begin{array} { l } { \text { The outer and inner diameters of a hemispherical } } \\ { \text { bowl are } 17 \mathrm { cm } \text { and } 15 \mathrm { cm } \text { respectively. Find the } } \\ { \text { ost of polishing it all over at } 25 \text { paisa per cm? } } \\ { \text { (Take } \pi = \frac { 22 } { 7 } ) } \end{array}

Answer»

Given,Outer diameter of the hemisphere 2r =17cm

r=17/2

Its Inner diameter 2r=15cm

r=15/2

[Note:- C.S.A:-Curved Surface Area]

Therfore outer C.S.A = 2*22/7*17/2*17/2

=454.142sq cm

Its inner C.S.A= 2*22/7*15/2*15/2

=343.571sq cm

Then 454.142+343.571=797.7134

Rate of painting it=25 paise=Rs. 0.25

Therefore, 797.7134*0.25=Rs.199.4275

Hence the cost of polishing the hemispherical bowl is Rs. 199.43 .