"Question 2 The inner diameter of a cylindrical wooden pipe is 24 cm and its outer diameter is 28 cm. The length of the pipe is 35 cm. Find the mass of the pipe, if 1 cm^3 of wood has a mass of 0.6 g.
Class 9 - Math - Surface Areas and Volumes Page 230"
Answers
VOLUME:
The space occupied by an object solid body is called the volume of the particular object solid body volume is always measured in cubic unit.
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Given: inner diameter= 24 cm
Inner radius (r1) = 24/2 = 12cm
Outer radius (r2) = 28/2 = 14 cm
length of pipe(h) = 35 cm
Volume of cylindrical wooden pipe = outer volume – inner volume
Volume of cylindrical wooden pipe= π(r2)²h – π(r1)²h
= 22/7 ×35 × (14²
- 12² )
[a²-b²= (a+b)(a-b)]
= 22/7 ×35 × (14 - 12) (14 + 12)
= 22/7 ×35 ×2 × 26
= 5720 cm³
Mass of 1cm³ of wood = 0.6g
Mass of 5720 cm³ of wood= (5720 * 0.6)g
= 3432.0 g= 3432/1000
[1kg= 1000g]
= 3.432 kg
Hence, the mass of the pipe=3.432 kg
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Hope this will help you....