Today we’re visiting either the 39th or the 40th state to join our country: North Dakota! We don’t know whether North or South Dakota became a state first. The President at the time, Benjamin Harrison, didn’t want either state bragging about being first, the way your older sibling might. So he shuffled the certificates that made them states and signed without looking. What we do know is that Mr. Bubble bubble bath was invented here, which might be more important. It also produces the most honey of any state. But what will really make you say “Holy Cow!” is Salem Sue. Salem Sue is the world’s largest statue of a Holstein cow, standing 38 feet tall, 50 feet long, and weighing 6 tons. That sure makes her easy to spot.

*Wee ones: *Holstein cows are black and white. Can you find 1 white object, 1 black object, and 1 object that is both black and white?

*Little kids: *If North Dakota was the 40th state, how many of our 50 states became states after it? *Bonus: *If 1 bottle of bubble bath can last you 10 days, but lasts a cow only 2 days, how many bottles of bubble bath will the cow use in the time you use 1?

*Big kids: *If an average Holstein cow stands 5 feet tall, how many cows would need to stand on each others’ shoulders to be taller than 38-foot tall Salem Sue?* Bonus: *If there are 1.75 million cows and there are twice as many cows as people in North Dakota, can North Dakota have more than 1 million people?

*The sky’s the limit:*If a bunch of people and cows have a bubble bath pool party, and there are 6 times as many hooves as feet in the pool, and 12 total bubble-bathers, how many people and cows are in the pool?

Answers:

*Wee ones: *Objects might include socks, shoes, bedsheets, cellphones…and for black and white together, printed pages from books!

*Little kids: *10 states. *Bonus: *The cow will use 5 bottles of bubble bath, because 2 + 2 + 2 + 2 + 2 = 10 days.

*Big kids: *8 cows, since that would make them 40 feet tall. *Bonus: *No, there would have to be at least 2 million cows to keep the 2:1 cow:people ratio.

*The sky’s the limit: *3 people and 9 cows. Since 1 cow has 2 times as many hooves as people have feet, you know that there must be 3 cows per person in order to have 6 times as many hooves as feet (the person has 2 feet, and that person’s cows have 12). That makes a set of 4 swimmers in total. If there are 12 swimmers, there are 3 of these sets. That gives us 3 people (1 per set) and 9 cows (3 per set, x 3). You can check: the 3 people have 6 feet, and the 9 cows have 36 feet, which is 6 times as much.

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.