Is the square root of 20 a rational number or irrational number

The square root of 20 is 4.472135955. This is an irrational number because rational numbers are repeating decimals. This is not a repeating decimal and it cannot be expressed as a fraction. So, it is in fact a irrational number. 

I hope this helps:)

A number is rational if it can be written in form a/b where a and b are integers and b is not equal to 0
integers are like -4,-3,-2,-1,0,1,2,3,4, etc

so
√20=2√5 which is irrational because we can't write it as a fraciton with only integers

also a rational number multilied by an irratinonal number=irrtaional
we know that the square root of any prime number will be irrational and 5 is prime so 2 times √5=rational times irrational=irrational

√20 is irrational