Reader question: What does it mean when people say things "don't add up"?

My comments:

Two and two don't add up to five. Two and two add up to four. Five is incorrect.

When numbers don't add up, they don't work out right. For example, if a survey claims that 35 percent of its respondents say "Yes", 35 percent of others say "No" and another 35 percent say "I don't know", those percentages don't add up. 35 percent plus 35 plus 35 equals 105 percent. That's impossible. And what does than mean? Well, something is wrong with that survey – it doesn't what it's talking about.

When people say things – theories for instance – don't add up, it means they don't make sense. Or in another saying, they don't hold water.

Hold water? Yeah, think of baskets with holes in the bottom. Baskets with holes in the bottom won't hold water. When theories are said to fail to hold water, they don't conform to logic¹. In the novel Strange Case of Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson, Mr. Utterson, the lawyer, contemplates² the disappearance³ of Mr. Hyde thus with Poole, the butler:

"This is a very strange tale, Poole; this is rather a wild tale, my man," said Mr. Utterson, biting his finger. "Suppose it were as you suppose, supposing Dr. Jekyll to have been – well, murdered, what could induce the murderer to stay? That won't hold water; it doesn't commend itself to reason."

Here are a few more up-to-date examples of things that don't add up:

1. Iraq's numbers don't add up, U.S. says (latimes.com, November 30, 2007).

2. Maths lessons don't add up for pupils (physorg.com, December 6, 2007).

3. Asian takeovers don't add up: Morgan (theaustralian.news.com.au, December 10, 2007).

4. AIDS figures, funds don't add up (in.news.yahoo.com, December 8, 2007).

5. Sister says findings in brother's death don't add up (knoxnews.com, November 22, 2007).

6. Arithmetic teacher's excuses don't add up (business.timesonline.co.uk, November 27, 2007).

7. Claims of vanishing middle class don't add up (deseretnews.com, December 5, 2007).

8. OOIDA says Mexican truck stats don't add up (tacitus13.newsvine.com, December 6, 2007).

9. My two cents don't add up to a penny on Technorati (technorati.com/blogs/patentpen21.livejournal.com, date unknown, no bother).

Ah well, apparently⁴ a lot of things don't add up when you put two and two together.

A lot of times in fact, it depends on how you put two and two together.