Month: July 2012

PEMDAS

Someone asked on Facebook: “5 + 5 + 5 – 5 + 5 + 5 – 5 + 5 × 0 = ?” Is it: (a) 40  (b) 0  (c) 20  (d) 15?

Take a moment to work it out. It’s not a trick question; it’s just arithmetic. Have you got it?

You will, of course, have seen that the problem could equivalently have been written as “5 + 5 + (5 – 5) + 5 + (5 – 5) + (5 × 0)”, which in turn is “5 + 5 + 0 + 5 + 0 + 0”, which is… 15.

As I write this, the Facebook poll shows these responses:

  • 2,225,250 answered 0 
  • 981,309 people correctly answered 15.
  • 518,062 answered 20
  • 86,759 answered 40

This is sad in so many ways. First and most obvious is that the majority of respondents answered incorrectly. It appears they ignored operator precedence (or “order of operations” rules), did the addition and subtraction first, and then multiplied the final result by zero.

But I’m willing to attribute this in part to the context. This isn’t a scientific survey (in any way), and the question’s title invites poor thinking. After the mathematical expression, the question adds “(I Bet More People Will Answer It Wrong :P) Give A Try !!”

This identifies the question as a trick, so instead of simply computing the answer mathematically many people will just scan for the trick. Spotting the “× 0” at the end, they’ll leap to the conclusion other people would not spot that, and then jump straight to the 0 answer without ever evaluating the rest of the expression. So some of those 2,225,250 wrong answers are not from people who have forgotten about operator precedence, but from people who just didn’t put a lot of thought into a Facebook poll.

I’m more interested in the other two wrong answers. More than half a million people answered “20” which I imagine means they missed the “× 0” entirely and did just the addition and subtraction. Worse, many arrived at 40 which I can only conclude is the result of counting the fives and ignoring the operators (and the 0) entirely — i.e., treating everything as addition.

Let’s just all keep this in mind the next time your local school district asks for more money.

Boy Scouts of (Un-)America

The Boy Scouts of America supposedly spent the past two years reevaluating whether to allow gay Scouts and volunteers to participate in their organization. They decided against it.

“The vast majority of the parents of youth we serve value their right to address issues of same-sex orientation within their family, with spiritual advisers, and at the appropriate time and in the right setting,” said Bob Mazzuca, chief scout executive of Boy Scouts of America.

This logic is baffling mostly because it necessarily implies that gay people cannot be in a room with children without talking about sex. Granting unequivocally that parents want to discuss sex and adult relationships privately with their own children at home, shouldn’t these protesters also be worried about the conversations your straight leaders are having?

Perhaps more importantly, though, this rationale assumes that absent direct contact with an actual, “real life” gay person, children will never hear about homosexuality outside their home. My daughter wasn’t in Kindergarten more than three months before she came home asking if two boys could ever get married. That’s what Kindergartners do!

In Kindergarten Cop, on Arnold Schwarzenegger’s first day in a Kindergarten classroom, a boy stands up and proudly proclaims, “Boys have a penis; girls have a vagina,” to giggles from the rest of the class. In my daughter’s actual classroom I heard similar assertions about death, politics, mathematics, religion, spelling, clothing, pets, and family relationships. And apparently, one day, someone took ten seconds at recess to announce that sometimes two boys will marry each other.

Sometimes sheltering children from the complexities of reality is useful and warranted, but attempting to shelter children from the diversity of other people they’ll inevitably encounter in adulthood is both futile and harmful. However much good the Boy Scouts might do (and they do some considerable good), our society cannot tolerate any group that teaches children to discriminate and to exclude.

Not coincidentally, while the Boy Scouts spent the last two years deciding gay people are worthy of their group, I’ve spent the last two years refusing to participate in their organization in any way. Let’s watch the Boy Scouts decline into obsolescence as more tolerant groups rise to take their place. Perhaps the more tolerant Baden-Powell Service Association is our first step?