Birthday Cards
Two birthday cards using modular arithmetic: mod 365 you're a newborn, or, pedantically, your age in days equals your number of leap years.
Use this cartoon
Free for classrooms, worksheets, slides and other non-commercial use under CC BY-NC 4.0, with credit to Ben Orlin.
Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2018-01-23-birthday-cards/ (CC BY-NC 4.0)Transcript
"Birthday cards for mathematicians!"
[Regular] "Modulo 365 days... you're a newborn!"
[Extra Pedantic] "Modulo 365 days... you are how many Leap Years you've lived through"