A favorite expression in our house is, “We all use math every day.” (It’s from the opening credits of the TV series, Numbers.)

Recently, I saw a quote from a newspaper in Missouri that said:

“The outdoor pool at the Kirksville Aquatic Center holds about 200,000 gallons of water.

“Compare that to the 33.4 million gallons of water the Atlantic Ocean holds, which means it would take about 167 outdoor pools to make one Atlantic Ocean.”

A woeful “we all use math every day” popped out of me.

“What’s up?” my wife asked, so I shared with her the ocean quote.

She realized, as I did, that the writer’s math was correct on one level, but hugely wrong on another.

If you multiply 200,000 gallons by 167, you will, in fact, get 33.4 million gallons. However, the 167 outdoor pool estimate for the size of the Atlantic Ocean was so absurd it made us laugh.

When we calmed down, I asked, “How many gallons of water do you suppose there really are in the Atlantic Ocean?”

Neither of us had a clue, so I looked it up. Or tried to. The answers varied from website to website. Some seemed plausible, but others were as absurd as the swimming pool estimate.

My wife and I decided to attack the problem on our own. We weren’t looking for an exact answer–which isn’t really possible–just an estimate we felt we could trust.

Our approach to finding the number of gallons in the Atlantic Ocean would consist of four simple steps. Figure out how many gallons there are in one cubic foot. Figure out how many cubic feet there are in a cubic mile. Multiply the two numbers to find how many gallons are in a cubic mile. Then multiply that by the number of cubic miles in the Atlantic.

Step one: A cubic foot holds 7.48 gallons. (We didn’t measure, we looked it up.)

Step two: There are 5,280 feet in a mile. So we multiplied 5,280 times 5,280 times 5,280 to find the cubic feet in a cubic mile. The answer: about 147 billion cubic feet.

Step three: We multiplied 7.48 gallons times 147 billion cubic feet and determined that there are around 1.1 trillion gallons of water in one cubic mile.

According to Wikipedia, there are about 75 million cubic miles of water in the Atlantic Ocean. Good enough for us.

Step four: We multiplied (aren’t cell phone calculators wonderful?) the 1.1 trillion gallons in one cubic mile times 75 million cubic miles. The answer? The Atlantic Ocean contains about 82 quintillion gallons of water. That’s 82 followed by 18 zeros.

How many Kirksville Aquatic Center swimming pools is that? Divide 82 quintillion by 200,000. The answer, trust me, is more than 167.

When we were done, my wife and I looked at each other. “We all use math every day,” she said. I smiled and nodded.

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