Question

36
Find the slant height of a right circular cone whose volume is 12936 cm and
radius of the base is 21 cm. Also find its total surface area.
एक लंबवृत्तीय शंकु की तिर्यक ऊँचाई ज्ञात कीजिए, जिसका आयतन 12936 घन सेमी है तथा
आधार त्रिज्या 21 सेमी है । इसका सम्पूर्ण पृष्ठीय क्षेत्रफल भी ज्ञात कीजिए ।​

Answer 1

Step-by-step explanation:

given:

Volume of the cone = 12936 cm³.

Radius = 21 cm.

Let the height be h cm.

Volume of cone= 1/3πr2h.

Volumeofcone= 1/3πr 2 h.

⟹ 1/3 πr2

h=12936

⟹h= π×21×21/12936×3

⟹h= π88

=88× 7/22

⟹h=4×7=28.

Slantheight(l)= h2 +r 2

= 282+21 /2

= 784+441

= 1225

=35cm.

Slantheight=35cm.

TotalSurfaceArea=πr(r+l).

= 7/22

×21(21+35)

=66×56=3696cm

2

.

TotalSurfaceArea=3696cm

.