Course Content
CBSE Class 8 Maths
About Lesson

1. Prime Factorization Method

  • Express the number as a product of its prime factors.
  • Pair the same prime numbers.
  • Take one number from each pair and multiply them.

Example:
Find √144 using prime factorization.
144 = 2 × 2 × 2 × 2 × 3 × 3
√144 = 2 × 2 × 3 = 12


2. Long Division Method

Used when the number is not a small perfect square.

Step 1: Pairing the Digits

  • Start grouping the digits of the number in pairs from right to left.
  • Each pair (or single digit in the case of an odd number of digits) will be processed in steps.

Step 2: Find the Largest Square

  • Identify the largest number whose square is less than or equal to the first group (or single digit).
  • Write this number as the quotient and the divisor.
  • Subtract its square from the first group and bring down the next pair of digits.

Step 3: Double the Quotient

  • Take the quotient, double it, and write it as the new divisor (without the last digit).
  • Find a digit that, when added to this divisor and multiplied by itself, is the largest possible without exceeding the number.

Step 4: Repeat the Process

  • Continue the process until all digits have been used.
  • If a decimal is needed, continue by adding pairs of zeros to the remainder and repeating the process.

3. Estimation Method

  • Identify two perfect squares between which the number lies.
  • Estimate the value between those two numbers.

Example:
Find √40.

  • 36 < 40 < 49
  • √36 = 6 and √49 = 7
  • Since 40 is closer to 36, √40 ≈ 6.3

4. Using Repeated Subtraction

For small perfect squares, subtract successive odd numbers until you reach zero. The number of steps taken is the square root.

Example: Find √16.
16 – 1 = 15
15 – 3 = 12
12 – 5 = 7
7 – 7 = 0

Since 4 steps were taken, √16 = 4.


These methods provide different approaches to finding square roots efficiently based on the type of number.

 

Conceptual Understanding of Square Roots of Decimals

Definition:
The square root of a number is a number such that:

y² =x

Methods to Find the Square Root of a Decimal:

  1. Convert to a Fraction:

    • Express the decimal as a fraction and find the square root of both numerator and denominator.

  2. Estimation Method:

    • Identify two nearby perfect squares.

  3. Long Division Method (For Precise Calculation):

    • A step-by-step approach similar to long division, used for non-perfect squares.

This approach ensures accurate calculations of square roots for decimal numbers.