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# The Equation for a Happy Mother's Day

What's the most important holiday in May? Obviously it's Mother's Day. But did you know there's an equation that can help you celebrate Mom? Keep on reading to find out what it is!

By
Jason Marshall, PhD
Episode #198

As we recently discovered, the first major holiday in May—Star Wars Day on May 4th—is full of math fun. But would you believe that the other big holiday in May—the much more important Mother's Day—is also chock-full o' math goodness?

Believe it or not, it is.

For example: How many mothers are there in the United States? How many children were born this year? What's the most common number of kids? And, most importantly, what's the equation for a happy Mother's Day? Those are exactly the questions we'll be answering today.

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## Mother's Day Stats and Figures

Holidays are great for those of us who love stats, figures, and all things quantitative. And Mother's Day is no exception. Here are a few of my favorite numbers that I discovered about mothers and Mother's Day by looking at recent United States Census data:

• There were approximately 85.4 million mothers in the United States in 2009.

• Approximately 4.1 million women between the ages of 15 and 50 gave birth in the last 12 months. According to Census data, there are about 76 million women in that age group in the United States, which means that a bit over 5% of those women gave birth in the last year!

• About 53% of women between the ages of 15 and 44 in the United States have children. 17% have one child, 20% have two children, 10% have three, and the remaining roughly 5% of women have four or more kids.

• The average age of women who gave birth for the first time in 2012 was… 25.8 years old.

More specific to Mother's Day, according to that same U.S. Census data, there are 15,307 florists, 12,403 employees of greeting card producers, and 23,397 jewelry stores in the United States that will be very busy leading up to Mother's Day this year…and every year.

## Moms Love Parametric Equations…Really!

And now it's time for today's main event. If I was to tell you that I know an equation that just might guarantee you a happy Mother's Day, would you be interested? Of course you would.

Actually, before I can reveal the "Happy Mom" equation in its full glory, we first need to spend a minute talking about something called a parametric equation. I know, I know—this might sound like a kind of strange and maybe even frightening thing to learn about for Mother's Day, but hang with me for a minute and I think you'll see that's it's really not so bad.

Equations containing two variables (such as those we've learned to graph) relate the value of one variable (often called x) to some other variable (often called y). For example, the equation y =x + 2 tells us how x and y are related—namely, y is always 2 greater than x. In other words, if we plug in some value for x, we get back some value for y as determined by the relationship set up by the equation.

But that's not the only way to express a relationship between two things like x and y. Because we can also write them using Mom's favorite method: the parametric equation. Which is…?