Mensuration Questions

Multiple choice
  1. $5:12$
  2. $12:5$
  3. $13:12$
  4. $5:11$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a right triangle is revolved about a leg, it forms a cone where the other leg is the radius and the revolved leg is the height. For the first case (revolved about 12cm), radius r1=5, height h1=12, volume V1 = (1/3) * pi * 5^2 * 12 = 100pi. For the second case (revolved about 5cm), radius r2=12, height h2=5, volume V2 = (1/3) * pi * 12^2 * 5 = 240pi. The ratio V1:V2 is 100:240, which simplifies to 5:12.

Multiple choice
  1. $4cm$
  2. $8\pi cm$
  3. $8cm$
  4. $16cm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The volume of the hollow sphere is (4/3) * pi * r^3. With r=4, volume = (4/3) * pi * 64 = 256pi/3. Half of this is 128pi/3. The volume of the cone is (1/3) * pi * R^2 * h. Setting (1/3) * pi * R^2 * 2 = 128pi/3 leads to 2 * R^2 = 128, so R^2 = 64 and R = 8.

Multiple choice
  1. $19.404$ litres
  2. $16.141$ litres
  3. $22.254$ litres
  4. $18.204$ litres
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Volume of a hemisphere = (2/3) * pi * r^3. With r = 21 and pi = 22/7, V = (2/3) * (22/7) * 21^3 = (2/3) * (22/7) * 9261 = 2 * 22 * 441 = 19404 cm^3. Since 1000 cm^3 = 1 litre, this is 19.404 litres.

Multiple choice
  1. $94$ paise
  2. Rs. $1.40$
  3. Rs. $9.40$
  4. Rs. $19.40$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Volume = l*b*h = 3x*4x*5x = 60x^3 = 60. So x^3 = 1, x = 1. Dimensions are 3, 4, 5 dm (0.3, 0.4, 0.5 m). Surface area = 2*(0.12 + 0.20 + 0.15) = 2*(0.47) = 0.94 sq m. Cost = 0.94 * 10 = 9.40 rupees.

Multiple choice
  1. $225 cm^{2}$
  2. $234 cm^{2}$
  3. $270 cm^{2}$
  4. $279 cm^{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A cube has 6 faces. If we glue cubes to 5 faces, we lose 5 faces of the original cube and 5 faces of the new cubes. Original surface area = 6 * 3^2 = 54. 5 new cubes added, each adds 5 exposed faces. Total surface = 54 + 5 * (5 * 3^2) - 5 * 3^2 (covered area) = 54 + 225 - 45 = 234.