No, actually 2/5 is equal to .4 which is perfectly rational. Irrational Numbers have an infinitely long decimal expansion. This is just one digit.
Any rational number divided by any other rational number gives another rational number. Having an infinitely long decimal expansion is a necessary but not sufficient criterion for irrationality... for example, 1/3 is rational, though its decimal expansion is the infinitely long 0.33333333...
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No. By definition, the ratio or fraction of any two integers is a rational number.
phi = [1+sqrt(5)]/2 sqrt(5) is irrational and so phi is irrational.
It is real and irrational.
No, 2/5 is a rational number because it can be expressed as a ratio of two integers. An irrational number cannot be expressed as a fraction.
4*sqrt(2) Rational multiples of irrational numbers are irrational. sqrt(2) is about 1.414, and 5/4 = 1.25 < 1.414... < 1.75 = 7/4 so 4*sqrt(2) is between 5 and 7, and is irrational.
5 squared is 5*5 is 25. 25 is not an irrational number.