To simplify any fraction, look for a common factor in the top number
and the bottom number. If you find one, divide the top and bottom
both by their common factor. Eventually, you reach the point where
their only common factor is ' 1 ' ... that's when it's in simplest form.
4 and 10 both have 2 as a factor.
When you divide top and bottom both by 2, you have 2/5 .
This is the simplest form of 4/10 .
None of this has anything to do with mayflies. You can use the same
process to simplify fractions in ANY situation where fractions arise.