Mary is proofreading an ebook. sometimes she has to scroll several pages at a time. which key on the numeric keypad will her scroll down page-wise?

Key 3.

Explanation:

It is key 3 because when the number lock is off, it can work as a page down key. She is complaining about having to scroll little by little, and key 3 scrolls down page by page, saving her from the struggle. Hope this helps :)