Reciprocal of a number is 1 divided by that number.
So the reciprocal of 5 is 1/5, for example.
A reciprocal is a number that you multiply by so that the result equals 1.
The easiest way to find it is to just flip the fraction over.
Example:
The reciprocal of 3 is 3 is the same as 3/1, so we flip and the reciprocal is 1/3.
The reciprocal of 4/5 is 5/4.