Great question! I once said torah on this as follows:
Count the syllables, including all the shva nas, in the following:
???? ??? ???? ???? ???? ???? ???? ????????
= 22
Now it says in the next posuk, ?? ??? ???? ????? ??
Which Rashi explains to mean that she said to herself:
?? ??? ????? ?? ????? ???
Count the syllables:
= 11
Altogether 22 + 11 = 33
Each one was a ???? made up of 3 ?????. So 99. Add a ???? and you have 100