CBSE Class 9 Mathematics Question 7 of 13

Surface Areas and Volumes — Question 2

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2
Question

Question 1(ii)

Find the volume of a sphere whose radius is 0.63 m.

Answer

Given,

Radius of the sphere (r) = 0.63 m

By formula,

Volume of the sphere = 43πr3\dfrac{4}{3}πr^3

Substituting values we get :

=43×227×(0.63)3=43×227×0.250047=8821×0.250047=22.00421=1.05 m3= \dfrac{4}{3} \times \dfrac{22}{7} \times (0.63)^3 \\[1em] = \dfrac{4}{3} \times \dfrac{22}{7} \times 0.250047 \\[1em] = \dfrac{88}{21} \times 0.250047 \\[1em] = \dfrac{22.004}{21} \\[1em] = \text{1.05 m}^3

Hence, the volume of sphere = 1.05 m3.

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Surface Areas and Volumes — Interactive Study Guide

Formula Master Table

SolidCSATSAVolume
Cube (a)4a²6a²
Cuboid (l,b,h)2h(l+b)2(lb+bh+hl)lbh
Cylinder (r,h)2πrh2πr(r+h)πr²h
Cone (r,h,l)πrlπr(l+r)⅓πr²h
Sphere (r)4πr²&frac43;πr³
Hemisphere (r)2πr²3πr²⅔πr³

Common Traps

Cone CSA uses slant height l, NOT height h! l = √(r²+h²)
Hemisphere TSA = CSA + base circle = 2πr² + πr² = 3πr²
Use radius, not diameter! If diameter is given, divide by 2 first.

Quick Self-Check

  1. Volume of cube with side 5 cm? (125 cm³)
  2. CSA of cylinder with r=7, h=10? (2×22/7×7×10 = 440 cm²)
  3. Volume of cone with r=3, h=4? (⅓×π×9×4 = 12π cm³)

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