When you borrow a book from the library, you need to bring it back within a few weeks so other people can borrow it, too. But sometimes people return their library books late — really, really late. Someone just found a library book that had been checked out for 65 YEARS! On top of it, it was found at the opposite end of the country. Wayne Hachey of Maine tripped over a copy of the famous book Gone with the Wind in his dad’s attic, and saw that it was a library book from John Rodgers High School out in Spokane, Washington. It was originally checked out in 1949, and at their late fee back then of 2 cents per day, it owed a $475 fine. However, the library didn’t make him pay the fine, because the book was printed in 1946 and is worth $350, since it’s so old and special. Clearly the library is happy to have it back!
Wee ones: What shape is the cover of most books, including this one?
Little kids: If Wayne had kept the book for another year to read it, how many years late would it have been? Bonus: If you owe 2 cents each day a book is late, how much do you pay for a whole week?
Big kids: Which year was longer ago, 1946 or 1949? By how many years? Bonus: Given that, how many years older than you is this book?
The sky’s the limit: If instead your library fine is 1 cent the first day, then another 2 cents for the 2nd day, then another 3 cents for the 3rd day…how much would you owe after 20 days? Do you know a trick to solve this?
Wee ones: A rectangle.
Little kids: 66 years. Bonus: 14 cents.
Big kids: 1946 was 3 years earlier. Bonus: Different for everyone…the book is 65+3 years old, or 68 years, so subtract your age from 68.
The sky’s the limit: When you add any long series like 1+2+3…+9+10+11…to 20, the numbers pair off: here the 10+11 add to 21, the 9+12 add to 21, the 8+13 add to 21…you end up with 10 sets of 21, which is 210 cents or $2.10. That’s one reason the formula for these “triangle numbers” (since you can stack each number of balls in rows to make a triangle) is the biggest number times 1 more than itself, divided by 2.