Which number is irrational?

A. 0.454545 ...

B. square root of 5

C. 0.777 ...

D. 0.3

is it square root of 5?

Yes, it is B.

You can express the others as fractions, but not the square root of 5.

Irrational numbers are number that can't be written in a/b form where a and b are integers and b≠0

if it repeats, it can be written as a fraction

if it terminates, it can also be written as a fraction

if you have a square root that doesn't simplify nicely, we assume it to be irrational

so

A. 0.454545=45/99

B. irrational

C. 7/9

D. 3/10

yep, it's √5