Course Content
CBSE Class 8 Maths
About Lesson
Adding Consecutive Odd Numbers:
  • The sum of the first few consecutive odd numbers forms a perfect cube:

  • The number of consecutive odd numbers required to form a cube is always equal to the base number of the cube.

  • For example, to obtain , we need 10 consecutive odd numbers.

2. Cubes and Their Prime Factors:

2.1 Prime Factorization of a Number and its Cube:
  • Observing the prime factorization of some numbers and their cubes:

  • Each prime factor of a number appears three times in the prime factorization of its cube.

2.2 Identifying a Perfect Cube:
  • A number is a perfect cube if each prime factor in its prime factorization appears three times.

  • Example:

    • 216: → Perfect cube ✅

    • 729: → Perfect cube ✅

    • 500: → Not a perfect cube ❌

3. Finding the Smallest Multiple that is a Perfect Cube:

3.1 Understanding the Concept:
  • Suppose we have a cuboid with dimensions 15 cm × 30 cm × 15 cm.

  • Volume of the cuboid:

    • 15×30×15 = 3×5×2×3×5×3×5

    • 2×3³×5³

  • To form a perfect cube, all prime factors must appear in multiples of three.

  • The missing factor is 2, so multiplying by 2 will make it a perfect cube.

  • The smallest multiple that makes this a perfect cube is 2 × Volume.

Conclusion:

  • Perfect cubes follow a pattern in summation and prime factorization.

  • Prime factorization helps in identifying whether a number is a perfect cube.

  • Multiplication by appropriate factors can make a number a perfect cube.