The square root of 45 is irrational. Why? Well, see below for an explanation!
A rational number includes any number that can be expressed as a whole integer; a fraction, a simple full number, and any form of a full number that isn’t a portion of a number. Because the square root of 45 is equal to more than 6 but less than 7, it is represented by a decimal. That decimal that represents it is 6 whole + a portion of another whole, meaning that the square root is not a perfect square. Imperfect squares, or numbers that can be divided to get only one number (such as 36 = 6 x 6), are irrational. Because 45 cannot be divided by a number to get that same quotient of the number being divided by, it is irrational. If you need any help, let me know and I will gladly assist you.