Square Root

# What Is the Square Root of 81? How To Find the Square Root of 81?

Written by Prerit Jain

Updated on: 12 Aug 2023

Contents

### What Is the Square Root of 81? How To Find the Square Root of 81?

The square root of 81 is 9. The square root of any number is just the inversion of squaring the given number. The number when multiplied twice gives the original value. For the given number 81, when the number 9 is squared 9^{2} or when multiplied twice by 9*9 we get 81.

For a perfect square number 81 finding the square root of the number is simple as they are whole numbers and not integers. Long division is used to find the square root of irrational and non-perfect square numbers. Since 81 can be the ratio of two numbers it is a rational number p/q, q = 0.

Looking to Learn Math? Book a Free Trial Lesson and match with top Math Tutors for concepts, homework help, and test prep.

**Methods to find the square root of 81**

Three methods are used to find the square root of a number that has perfect squares(here 81),

- Long division method
- Repeated subtraction method
- Prime factorization method

**Long division method**

Finding the divisor for the long division method is much simpler than those that are imperfect squares. When 9 is multiplied twice it gives 81 hence, the number 9 is used as a divisor.

Hence, the **√81 = 9**

**Repeated subtraction method**

Using the repeated subtraction method, the square root of the number can be easily solved but consumes time. Hence, the prime factorization and the long division method are widely used to find the square root of the number.

Start subtracting the given number by the first odd number, take the given value, and further subtract the number with the next odd number repeat the step until you reach zero.

- 81 – 1 = 80
- 80 – 3 = 77
- 77 – 5 = 72
- 72 – 7 = 65
- 65 – 9 = 56
- 56 -11 = 45
- 45 -13 = 32
- 32 -15 = 17
- 17 – 17 = 0

The last step in which zero is obtained is the 9th step.

Hence, the **√81 = 9**

**Prime factorization method**

Prime factorization is one of the simplest methods used to find the square root of a given number. Take the prime factor of the number as n square the given number we get n^{2}, take a single value, and multiply with the other square. By doing so we will get the square root of the number.

**Step 1: Find the prime factor of 81**- 81 = 3 × 3 × 3 × 3
**√**81 = (**√**(3 × 3 × 3 × 3))^{2}

**Step 2: Find the square of the similar factors by grouping them**

**√**81 = 3 × 3

**Step 3: By multiplying the common factors we get the square root of the number**- √81 = 9

**Solved examples**

**Example 1: What is the sum of the square of 81 and the square root of 81?**

Square of 81= 6561

The square root of 81 = 9

The sum of the square of 81 and the square root of 81 = 6561+9 = 6570

**Example 2: Karen wants to find the square root value of 9/81 to help him solve the sum**

The **√**9 = 3.

The **√**81 = 9

Therefore, the **√**9/81 = 1/3.

**Example 3: Solve 2 √81 + 2√81**

The

**√**81 = 9.

Hence 2 (9) + 2 (9).

= 18+18

=36.

**Example 4: what is the area of the square whose each side is equal to 9cm**

Area of the square = x^{2}

Here x= 9

Therefore, 9^{2} = 9*9 = 81

Hence the area of the square with 9cm = 81 sq. cm.

Looking to Learn Math? Book a Free Trial Lesson and match with top Math Tutors for concepts, homework help, and test prep.

**Frequently asked questions**

**What is the square root of 81?**

The square root of 81 = 9.

**Explain why the square root of 81 is a rational number.**

When finding the prime factor of 81 we get 9^{2} which is entirely an even power and hence all the numbers are positive integers which makes them rational numbers.

**What is the value of 9 and the square root of 9**?

The square root of 81 is 9, therefore 81**√**81 = 9*81 = 729

**What is the real value for the square root of 81?**

The actual value for the **√**81 = 9

**What is the square root of 1?**

The square root of 1 = 1

**What is the square root of (-81)?**

The square root of minus digits is imaginary numbers or imaginary units which really don’t have a square root.

**Is 81 a perfect square number?**

Yes, 81 is a perfect square number because they give the whole numbers when divided

Written by by

Prerit Jain