286 is the sum of the series below. You can plug this in or use long addition.
Either that or you make an average and that's your answer.
Can salvage 15c+ -15c is 0 + 8 is still 0
So each book is an average of 2.8 cm
so 120 divided by each book=number of books
120/2.8=42.85
round down since you can't fit .85 of a book on a shelf
the answer is 42 books
