Which number is irrational?

A. 0.454545 ...

B. square root of 5

C. 0.777 ...

D. 0.3

is it 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

Yes, it is B.

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