Ex 13.7, 2
Find the capacity in litres of a conical vessel with
radius 7 cm, slant height 25 cm
Given Radius of cone = r = 7 cm
Slant height = l = 25 cm
Let height of cone = h cm
We know that
l2 = h2 + r2
252 = h2 + 72
252 – 72 = h2
h2 = 252 – 72
h2 = (25 – 7) (25 + 7)
h2 = (18) (32)
h = √("18(32)" )
h = √("(9 × 2) × (32)" )
h = √("(9) × (64)" )
h = √("(32) × (82)" )
h = 3 × 8
h = 24 cm
Capacity = Volume of cone = 1/3πr2h
= 1/3 × 22/7 × 7 × 7 × 24 cm3
= 22 × 1 × 7 × 8 cm3
= 1232 cm3.
= 1232 × 1/1000 litres
= 1.232 litres

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.