Square root of 81

If you are looking to answer the following questions: “what is the square root of 81?” The answer is 9. 

ANSWER: square root of 81=9

The square root of a number (81 in this case) is a number (9 in this case) which multiplied by itself equals the number from which you are calculating the square root (81). Mathematically square root of 81 can expressed in the radical form or an exponent form as shown below:

  • Radical form of the square root of 81: √81
  • Exponent form of the square root of 81: (81)½ or (81)0.5

This symbol is called radical sign or radix. The number whose square root is being calculated is called the radicand. The radicand is the number underneath the radical sign (radix), in this case it is 81.

Square root calculation explainer video

 

Square root of 81 calculator

If you would like to confirm the answer to the question of “what is the square root of 81?” or calculate a square root of any other number use the square root calculator:

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Square root of 81 calculation guide

In the following sections we explain how to calculate the square root of 81. We will answer such common questions as: “is the square root of 81 rational or irrational?” and “is 81 a perfect square?” We will discuss what the principal square root of 81 is.  For your reference we also included the following tables:

  • Nth roots of 81
  • Perfect square numbers
  • Square roots of numbers around 81 

You will find all the information you need on the square root of 81 calculations below. 

What is the square root of 81?

The square root of 81 is a number which multiplied by itself equals 81. Therefore, the square root of 81 is 9 and we write it √81=9 because 92=81. Since 92 is the same as 9 x 9 the following expressions is true:

81 = 92=9×9

Therefore

ANSWER: square root of 81=√81=9

Is 81 a Perfect Square?

A number is considered a perfect square if it is a product of squaring a whole number (called integer). 0, 1, 2, 3, 4, 7, 8, and 9 are all whole numbers (same as integers). Numbers such as -8, 7.025, or 5 ½ are not whole numbers. Remember squaring is when a number is multiplied by itself. For example, 81 is a perfect square because it is a product of 92 which is the same as 9×9. Notice 9 is a whole number (integer).

In our example the square root of 81 is 9. Since 9 is a whole number therefore 81 is a perfect square.

ANSWER: 81 is a whole number 

Is the square root of 81 rational or irrational number?

A number is rational when it can be made by dividing a whole number by a whole number. A whole number which is also called an integer does not have a fractional part itself. Simply said a number is rational if it can be written as a fraction. 

A quick method to determine if 81 is a perfect square. The square roots of perfect squares are all rational numbers. The square roots of numbers that are not a perfect square are all irrational numbers. Since we know that 81 is a perfect square therefore 81 is a rational number.

Principal square root of 81

Every positive number has two square roots. One of the square roots is positive and another one is negative. For example the square roots of 81 are -9 (negative) and +9 (positive) because  (-9)^2=(+9)^2=81. The positive square root is denoted as “the principal square root”. Typically, when we are calculating “the square root of a number” we mean the principal square root. In our case it is positive 9 or +9 which is written as 9. As you may know if there is no minus (-) sign before a number it is a positive number. 

Again the principal square root of 81 is 9.

Calculating the square root of 81 with a calculator

In order to calculate the square root of 81 with a basic or a scientific calculator you need to enter 81 and then press the key with this sign  “√x”

√81 = 9

Calculating the square root of 81 in Excel and Google Sheets

There are two functions you can use to do this calculation. You can use the function SQRT () to calculate the square root of any number in Excel and Google Sheets. Click on a cell and type =SQRT(81). Hit enter. You will get 9.

You can also use the POWER function which works like an exponent is an equation. To find a square root of 81 type =POWER (81, 1/2). Remember square roots can be expressed as exponents as we discussed earlier in this article.

Table: Nth roots of 81

In the section above we explained how the square root (which is the 2nd root) of 81 is calculated. However there are more roots of 81. Find the Nth roots of 81 in the table below:

 

Index (N)Nth Root of RadicandExpressionRoot
2Square Root of 81²√819.000
3Cube Root of 81³√814.327
4Forth Root of 81⁴√813.000
5Fifth Root of 81⁵√812.408
6Sixth Root of 81⁶√812.080
7Seventh Root of 81⁷√811.873
8Eight Root of 81⁸√811.732
9Nineth Root of 81⁹√811.629
10Tenth Root of 81¹⁰√811.629

Table: Square root of numbers around 81

This table lists numbers around 81 and their respective square roots.

NUMBERSQUARE ROOT
768.718
778.775
788.832
798.888
808.944
819
829.055
839.110
849.165
859.220
869.274

 

Table: Perfect square numbers

This table lists perfect square numbers from 1 through 10,000.

Perfect SquaresSquare RootWhole Number (Integer)
1sqrt 1 =1
4sqrt 4 =2
9sqrt 9 =3
16sqrt 16 =4
25sqrt 25 =5
36sqrt 36 =6
49sqrt 49 =7
64sqrt 64 =8
81sqrt 81 =9
100sqrt 100 =10
121sqrt 121 =11
144sqrt 144 =12
169sqrt 169 =13
196sqrt 196 =14
225sqrt 225 =15
256sqrt 256 =16
289sqrt 289 =17
324sqrt 324 =18
361sqrt 361 =19
400sqrt 400 =20
441sqrt 441 =21
484sqrt 484 =22
529sqrt 529 =23
576sqrt 576 =24
625sqrt 625 =25
676sqrt 676 =26
729sqrt 729 =27
784sqrt 784 =28
841sqrt 841 =29
900sqrt 900 =30
961sqrt 961 =31
1024sqrt 1024 =32
1089sqrt 1089 =33
1156sqrt 1156 =34
1225sqrt 1225 =35
1296sqrt 1296 =36
1369sqrt 1369 =37
1444sqrt 1444 =38
1521sqrt 1521 =39
1600sqrt 1600 =40
1681sqrt 1681 =41
1764sqrt 1764 =42
1849sqrt 1849 =43
1936sqrt 1936 =44
2025sqrt 2025 =45
2116sqrt 2116 =46
2209sqrt 2209 =47
2304sqrt 2304 =48
2401sqrt 2401 =49
2500sqrt 2500 =50
2601sqrt 2601 =51
2704sqrt 2704 =52
2809sqrt 2809 =53
2916sqrt 2916 =54
3025sqrt 3025 =55
3136sqrt 3136 =56
3249sqrt 3249 =57
3364sqrt 3364 =58
3481sqrt 3481 =59
3600sqrt 3600 =60
3721sqrt 3721 =61
3844sqrt 3844 =62
3969sqrt 3969 =63
4096sqrt 4096 =64
4225sqrt 4225 =65
4356sqrt 4356 =66
4489sqrt 4489 =67
4624sqrt 4624 =68
4761sqrt 4761 =69
4900sqrt 4900 =70
5041sqrt 5041 =71
5184sqrt 5184 =72
5329sqrt 5329 =73
5476sqrt 5476 =74
5625sqrt 5625 =75
5776sqrt 5776 =76
5929sqrt 5929 =77
6084sqrt 6084 =78
6241sqrt 6241 =79
6400sqrt 6400 =80
6561sqrt 6561 =81
6724sqrt 6724 =82
6889sqrt 6889 =83
7056sqrt 7056 =84
7225sqrt 7225 =85
7396sqrt 7396 =86
7569sqrt 7569 =87
7744sqrt 7744 =88
7921sqrt 7921 =89
8100sqrt 8100 =90
8281sqrt 8281 =91
8464sqrt 8464 =92
8649sqrt 8649 =93
8836sqrt 8836 =94
9025sqrt 9025 =95
9216sqrt 9216 =96
9409sqrt 9409 =97
9604sqrt 9604 =98
9801sqrt 9801 =99
10000sqrt 10000 =100

Visit squarerootof.net for any square root related calculations including square roots, negative square roots, square roots from fractions, exponentiation and other related calculations.

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