Saved Bookmarks
| 1. |
(a)The total surface area of a right circular cone of slant height 13cm is 90¡Calculate(i)itsradiusfiijvolume in in terms of rtCalculate(ilit |
|
Answer» Total surface area of right circular cone = π r ( l + r ) ▪ On putting the values , we get :- ==> π r ( 13 + r ) = 90 π cm^2 ==> r ( 13 + r ) = 90 cm^2 ( both sides r divided by π ) ==> 13r + r^2 = 90 ==> r^2 + 13r - 90 = 0 On solving , we get ==> r^2 + 18r - 5r - 90 = 0 Taking common :- ==> r ( r + 18 ) - 5 ( r + 18 ) ==> ( r - 5 ) ( r + 18 ) ==> ( r - 5 ) = 0 , ( r + 18 ) = 0 ==> r = 5 and ==> r = -18 ( can not be negative ) __________________________ Hence , it's radius is 5 cm.__________________________ ques. = 2 ( To find it's volume ) We have , ● Radius = 5 cm ● Slant height , l = 13 cm ● height = ? ☆ h =√ l^2 - h^2 On putting values , ==> h =√ 13^2 - 5^2 ==> h = √ 169 - 25 ==> h = √ 144 ==> h = 12________________________ Volume of the cone = 1 / 3 π r^2 h cm^3 ==> 1 / 3 * 3.14 * 5^2 * 12 ==> 1 / 3 * 3.14 * 25 * 12 ==> 3.14 * 25 * 12 / 3 ==> 3.14 * 25 * 4 ==> 3.14 * 100 ==> 314 cm^3. Like my answer if you find it useful! |
|