Q: Is the square root of 21 a rational number?

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Rational.

Any number that is presented as an integer "over" (aka divided by) an integer is automatically a rational number - that's what the definition of a rational number is.

Some are and some are not. For example, the square roots of 2.25, 3.61, 4, 4.84, 5.29, 6.76, 7.29, 8.41, 9, 10.89, 11.56, 12.25, 13.69, 14.44, 15.21, 16, 17.64, 18.49, 19.36, 20.25, 21.16, 22.09, 23.04, 24.5025, and 25 are all rational numbers. But the square roots of 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, and 24 are irrational numbers. We believe, but can't prove easily, that there are more irrational square roots than rational ones.

Yes because it can be expressed as a fraction in the form of 21/2

You wont be able to add a rational number and an irrational number and get a number not in a fraction ( 3 + 22/7) (21/7 + 22/7 = 43/7) So, yes as you see in the example above it made another irrational number.

Related questions

No because it is 2 times the square root of 21 which is an irrational numberThe square root of 84 is not a rational number

Yes because 21 is a rational number

irrational

No, they are not.

It is equal to 21/2 which is a rational number

irrational, it has a never ending decimal

First note that 84=4x21 and 4 is a perfect square. So square root of (84)=square root (4x21)=Square root (4) Square root (21)= 2 multiplied by the square root of 21. You can also write this using rational exponents, but this is not in radical form. It is an equivalent expression, however. 2 x (21)1/2

The square root of 21 is 4.58257569495584.

The square roots of 21 are 4.5826 (rounded) and the negative of the same number.

It is: 2 times the square root of 21 and it's an irrational number

If the reverse square root of the reverse of square of a number is the number itself then it is Adam Number. For ex., 12 and 21 Take 12 square of 12 = 144 reverse of square of 12 = 441 square root of the reverse of square of 12 = 21 The reverse square root of the reverse of square of 12 = 12, then number itself. Such number is called Adam Number. cool....................

21 is a rational number.