On a busy road, the traffic can stretch for miles and miles. And that’s just one road in one town…imagine how many cars are on all the roads in your country! Our friend Abigail T. went even bigger: she asked us, how many cars do we have in the whole world? (and painted a picture of herself riding around in one!) Well, there are more than 1 *billion* cars out there (1,000,000,000). A million is a thousand thousands, and a billion is a thousand millions, so that’s a huge number. In the U.S. alone, there are 245 million cars for just 320 million people!

*Wee ones:* If you just count 4 blue cars on the road, what number do you say before 4?

*Little kids:* If 5 houses on your block each have a 2-car garage, how many cars can they hold together? Count up by 2s! *Bonus:* If on the road the 1st car in front of you is red, then the 4th car, then the 7th car…what’s the next red car to keep up the pattern?

*Big kids:* If people in your town bought 100 new cars this month, but 91 old cars went to the junkyard, how many more working cars are there now than a month ago? *Bonus:* If every U.S. car owner had 2 cars of those 240 million, how many people would have cars — and how many of the 320 million Americans would NOT have a car?

*The sky’s the limit:* There were 500 million cars in 1986, so it doubled by 2010. If it always takes the same amount of time to double, when will we have 4 billion cars?

Answers:

*Wee ones:* 3.

*Little kids:* 10 (2, 4, 6, 8, 10). *Bonus:* The 10th car, since every 3rd car is red.

*Big kids:* 9 more cars. *Bonus:* Only 120 million people would have a car, so 200 million would not.

*The sky’s the limit:* The year 2058. It took 24 years to double that 1st time. To reach 4 billion, we need to double from 1 to 2 billion, then from 2 to 4 billion. Each of those 2 jumps takes 24 years, for a total of 48 years after 2010.

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.