Is 2/5 greater than 1/2

No. 1/2 is (two and a half) / 5. That's more than (two) / 5.

The answer can come easily if you look at it this way: Make 1/2 and 2/5 have the same denominator, then multiply the numerator depending on how many times the denominator went into the number (I usually multiply the commentators by each other). Then you have 5/10 and 4/10. So 1/2 is bigger. Hope this clears things up!