Well you could ask yourself how many halves are in 1. And there are 2 halves in 1. so that means you could now say that for ever 1 whole number there are 2 halves.
next you ask yourself what if I have 2 whole numbers. well you can say now you have 2 whole and 2 halves for each whole. this means 1 * (2 halves) + 1 * (2 halves) = 4 halves.
we could do this all the way up to 11 and 1 half but there is something to notice. If if you have 2 whole and 2 halves for each whole this translates to 2 * (2 halves) = 4
see how they end up being the same answer but this one can be written much easier when dealing with larger numbers like 11.
so we can say: 11 wholes * (2 halves) = 22 halves
But but don't forget the extra 1/2 from 11 and 1/2
so the answer after adding the last one in is 23 halves