When Two Plus Two Equals Five – a poem by Kate Rauner

Two plus two is four.

That’s such a narrow view.

It always works in textbooks

Where reality is skewed.

But in the real world,

Anywhere that counts,

Measurements are iffy;

You’ve problems to surmount.

An error band surrounds

Every measurement you take,

It confuses and it obfuscates

The reckonings you make.

Significant figures

Define accuracy,

Where rounding is an issue

And precision is a key.

So if you measure two-point-four,

Don’t round it down to two

And add it next to two-point-three

And think that you are through.

Two-point-four and two-point-three

Sum to four-point-seven;

You may round that up to five

Without a math transgression.

So now you see that four’s

Not always two plus two;

They sometimes sum to five

For large enough values.

Thanks to one of my favorite sites, straightdope.com, where Cecil recently reminded me of an old math joke: 2 + 2 = 5 for large enough values of 2. Here’s another one:

Mathematicians at a conference take a break at the bar.

“This is a real math town,” says one. “Everyone here knows math.”

“I bet our bartender doesn’t know that the integral of X squared is one third X cubed,” says a second mathematician.

They bet and when the bartender comes over to take their orders, they ask her:

What’s the integral of X squared?

She smiles and says: “One third X cubed plus a constant.”

I haven’t tried to make that one into a poem yet.