# Friday the 13th

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

# Friday the 13th

November 13, 2015

Today is a Friday the 13th, a day that a lot of people think is unlucky. Is it really worse than any other day? Actually, there are very few really bad Fridays the 13th in history…we have a few of them every year, so if they were always unlucky, we would know by now. For centuries people have thought the number 13 itself was unlucky, meaning it would make bad things happen. That fear is called triskaidekaphobia, and it’s the reason many tall buildings don’t call their 13th floor the 13th floor. They actually skip from 12 to 14. Check it out the next time you’re in an elevator. The truth is, numbers can’t be lucky or unlucky — they’re just numbers. Really, the only thing to fear about Friday the 13th is trying to spell “paraskevidekatriaphobia.”

Wee ones: If the 13th is a Friday, what day of the week will the 14th be?

Little kids: Can you count backwards from 13 down to 1? Try it!  Bonus: If you count from 1 to 13, how many numbers have a 1 in them?

Big kids: If a month has a Friday the 13th, what dates are the other Fridays that month?  Bonus: If the month of your birthday has a Friday the 13th, what day of the week is your birthday?

Answers:
Wee ones: Saturday.

Little kids: 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1.  Bonus: 5 of the numbers have a 1: they are 1, 10, 11, 12, 13.

Big kids: The other Fridays are the 6th, 20th, and 27th.  Bonus: Different for everyone: figure out how many days your birthday falls before either 6, 13, 20, or 27, and use that to count backwards through the weekdays. If your birthday actually is the 13th, watch out!

### Laura Overdeck

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.