Hi Purnima,
One of the ways you can probably do that is to highlight all the rules that you need to approve and export them if they are in one problem. Then when you import them you can select "overwrite" and "automatically approve".
If these 100 validation rules are already an extract that you are going to import then you use the same process and they all will be automatically approved.
I have not tried approving them en-masse but if you are the administrator you should be okay.
Let me know if this works for you.
Thanks