NCERT Solutions for Class 9 Maths Chapter 13

Important NCERT Questions

Surface Areas and Volumes

NCERT Books for Session 2022-2023

CBSE Board, UP Board and Other state Boards

EXERCISE 13.7

Page No:233

Questions No:2

(i) radius 7 cm, slant height 25 cm

(ii) height 12 cm, slant height 13 cm

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(I) Radius of conicon vessel r = 7 cm and slant height l = 25 cm.

Let, the height of conical vessel = h cm

We know that, l² = r² + h²

⇒ 25² = 7² + h²

⇒ 625 = 49 + h² ⇒ h² = 625 – 49 = 576

⇒ h = √576 = 24 cm

Capacity of conical vessel = 1/3πr²h

= 1/3 × 22/7 × 7 × 24 = 1232 cm³ = 1232/1000 = 1.232 litres

Hence, the capacity of conical vessel is 1.232 litres.

(II) Height of conical vessel h = 12 cm and slant height l = 13 cm

Let, the radius of conical vessel = r cm

We know that, l² = h² + r²

⇒ 13² = 12² + r²

⇒ 169 = 144 + r²

⇒ r² = 169 – 144 = 25 ⇒

r = √25 = 5 cm

Capacity of conical vessel = 1/3πr²h

= 1/3 × 22/7 × 5 × 5 × 12 = 2200/7 cm³

= 2200/(7×1000) = 11/35 litres

Hence, the capacity of conical vessel is 11/35 litres.