This Week From Bedtime Math: The World's Favorite Number

Odds are, you have a favorite number though it might be even! How many people share your favorite integer? Find out in this digit-al math challenge.
By Laura Overdeck
Oct 07, 2014



Oct 07, 2014

What is Bedtime Math? A message from Laura: Bedtime Math is a pretty simple idea: We all know we should read to our kids at night, but what about math? My husband and I have done fun, mischief-loaded math problems with our kids at night for years, and when at age 2 our third child started hollering for his own math problem, we realized we were onto something:  In a world where so many people say, "Ewww, math!" we had created a household culture where kids don't just tolerate math, they actually seek it out. Now, every week, we'll be posting a new problem right here on Scholastic Parents!
Do you have a favorite number? What is it? And have you ever wondered what everyone else's favorite number is? Someone had to study this, of course, with over 30,000 people voting online for their favorite number. The number chosen by the most people is…drum roll…7! Other small numbers did well, too: almost half of all people chose numbers between 1 and 10. The second-place number was 3, followed by 8, 4, 5, 13, 9, 6, 2, and 11, to round out the top ten choices. Interestingly, all numbers between 1 and 100 were chosen by someone: the number 39 has fans, as does 53, 62, or any of the others. In fact, the lowest number not chosen by anyone was the number 110: apparently other numbers ending in 0 weren't popular either. People's reasons for their favorites were pretty funny: many said the number was their birthday, but some gave reasons such as "I like it because it's squiggly" (for the number 2). The point being, whatever your favorite number and whatever your reason, someone else out there probably likes it, too.

Now see if your kids can come up with the right  solutions to these math problems:

Wee ones: Do you have a favorite number, and can you count that high? Or pick any number you like and try counting up to it!

Little kids: If you and 9 friends all vote on your favorite numbers, how many votes is that?  Bonus: If the top 10 favorite numbers include 7, 3, 8, 4, 5, 9, 6, and 2, which of the 10 single digits are missing from that list?

Big kids: If of the 30,000 people surveyed, exactly half of them pick numbers between 1 and 10, how many votes is that?  Bonus: The number 7 got about 1/10 of all votes. If it had received exactly 1/10, and 3 (the second favorite) had gotten half as many, how many votes would they get altogether out of 30,000 people?

The sky's the limit: If your favorite number has 2 digits, neither of which is prime on its own, and when you reverse the digits the new number is 27 more than your favorite, what's your favorite number?
Wee ones: Different for everyone…see how high you can go!

Little kids: 10 votes.  Bonus: 0 and 1.

Big kids: 15,000 people.  Bonus: 4,500 votes.

The sky's the limit: 69. If you reverse the digits and get a number that's 27 more, the two digits have to be 3 apart (since the 10s digit jumped by 3 but the single digit dropped by 3). That means one digit is even and one is odd. All even digits are non-prime (composite), but the only odd digit that isn't prime is 9. So the other is 6, giving you 69.  And, as fan Les C. pointed out, although the number 1 is not composite, it's not prime either, so 41 and 14 could be a solution as well. Thanks for the astute catch!

If you want more fun math and an excuse to play with your food, check out Bedtime Math's latest video on Science Friday to see how waffles and math add up!

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