Chapter 1 · CBSE Class 8 Maths (NCERT Ganita Prakash Part 1)

A Square and A Cube

Explore square numbers and cube numbers, learn to spot patterns in them, and find square roots and cube roots using prime factorization.

⬜ Chapter 1

1.1

Square Numbers and Their Patterns

A square number is the product of a number multiplied by itself. Square numbers show interesting patterns — like always ending in specific digits, and being the sum of consecutive odd numbers.

1

Is 144 a perfect square? Find its square root.

Yes; 144 = 12×12, so √144 = 12

2

Find the sum of the first 5 odd numbers and relate it to a square number.

1+3+5+7+9 = 25 = 5²; the sum of the first n odd numbers is always n²

1.2

Cube Numbers and Cube Roots

A cube number is a number multiplied by itself three times. Cube roots can be found using prime factorization by grouping prime factors in triples.

1

Find the cube root of 216 using prime factorization.

216 = 2×2×2×3×3×3 = 2³×3³; grouping in triples gives ∛216 = 2×3 = 6

2

Is 100 a perfect cube?

No; 100 = 2²×5², and the prime factors can't be grouped into triples, so 100 is not a perfect cube

Practice

Exercises

1. Find the square root of 225 using prime factorization.

2. Is 128 a perfect square? Explain.

3. Find the cube root of 512.

4. Find the sum of the first 6 odd numbers and identify the square number.

5. Is 1,000 a perfect cube? Find its cube root if so.

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