The Total solution for NCERT class 6-12
Heightof the cone (h) = 21 cmSlant height (l) = 28 cm∴ l2 = r2 +h2⇒ r2 = l2–h2 = (28)2 –(21 )2⇒ 784 –441 = 343 …(i)Now area of base = πr2= x343 [From (i)]
= 22 x 49 = 1078 cm2