Is 0.4 the decimal equivalent of 0.40?

Well, honey, technically speaking, 0.4 and 0.40 are both decimal numbers, but they ain't exactly the same. You see, 0.4 is the same as 0.40 when it comes to value, but adding that extra zero at the end just makes it look fancier - like putting a bow tie on a cat. So, in short, yes, 0.4 is the decimal equivalent of 0.40, but one just likes to show off a bit more.