Exercise 9.2 | Chapter 9 Mensuration | NCERT RBSE CBSE | Class 8 Maths

Mann Ki Ganit2 minutes read

The text discusses various formulas and calculations related to determining surface areas, paint requirements, and conversions, with examples provided for better understanding. Key points include calculating surface areas of different shapes, determining paint can requirements, and converting units of measurement accurately.

Insights

  • The formula for calculating the total surface area of a cuboid cartoon involves adding the areas of its length, breadth, and height, with an example yielding a total surface area of 60 units. The total surface area of the cuboid cartoon in question is found to be 15000 cm square.
  • Converting measurements from centimeters to meters involves dividing by 100, such as transforming 750 cm to 7.5 meters. Additionally, the area of a circle can be calculated using the formula A = πR^2, with the radius (R) being half the diameter, as shown in an example resulting in 154 square centimeters.

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Recent questions

  • How is the total surface area of a cuboid calculated?

    By adding the areas of length, breadth, and height.

  • What is the formula for finding the number of paint cans needed?

    Derived from the painted area calculation.

  • How is the literal surface area of a cylinder calculated?

    Using the formula 2πrh.

  • How is the perimeter of a rectangle calculated?

    By performing further calculations after determining the area.

  • How do you convert centimeters to meters?

    By dividing by 100.

Related videos

Summary

00:00

Calculating Surface Areas and Paint Needs

  • In Excel 11.3, the question involves a figure with different sizes, determining Lata if there's a one-point difference, and otherwise, when it's considered yours.
  • To minimize material usage, the total surface area of a cuboid cartoon must be calculated by adding the areas of length, breadth, and height.
  • The formula for finding the total surface area is Lb + Bh + Hl, with an example calculation resulting in 60.
  • The total surface area of the cuboid cartoon is found to be 15000 cm square.
  • To paint the outside of a cabinet, the area of the four walls and the top must be calculated, with the formula being L + B + H or by mincing the bottom.
  • The formula for finding the number of paint cans needed is derived from the painted area calculation, resulting in 150.
  • The literal surface area of a cylinder is calculated using the formula 2πrh, with an example yielding 154 cm square.
  • The total surface area of a hollow cylindrical shape is found using the formula 2πrh + r, with a calculation resulting in 44.
  • Cutting a cylinder in half reveals a rectangle with an area of 424, leading to the formula for finding its length and breadth as 4224/33.
  • The perimeter of the rectangle is calculated to be 128, with further calculations leading to a length of 750 meters.

39:24

Converting cm to meters and calculating areas

  • To convert centimeters to meters, divide by 100. For example, if you have 750 cm, dividing by 100 gives you 7.5 meters. In another scenario, if the diameter of a circle is 14 cm, the radius (R) would be half of that, which is 7 cm. The area of the circle would then be calculated using the formula A = πR^2, with the result being 154 square centimeters.
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