We can tear the remaining pages and staple/bind  it together and make it as our running notes/reference book etc.
its only one point but hope it helps you.
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Yes, donating our old books and notebooks is a very good thing as this can help some needy children in their studies. Some ways to do this are - You can donate your books in some association or some NGO which works for poor or needy children. Another way is that you can donate your books and notebooks in a school which teaches poor children. These ways can help a lot.
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