Even Older Man Yells at Whippersnappers

[Steve D'Aprano]

On Wed, 20 Sep 2017 04:48 am, Larry Martell wrote:

>>> It was my birthday the other day. People at worked asked how old I
>>> was. I replied:
>>>
>>> ((3**2)+math.sqrt(400))*2
>>>
>>> Quite a few people somehow came up with 47. And these are technical people.
>>
>> *headscratch* Multiple people got 47? I'm struggling to figure that
>> out. If they interpret the first part as multiplication (3*2 => 6),
>> that would get 26*2 => 52; if they don't understand the square
>> rooting, they'd probably just give up; if they ignore the parentheses,
>> that could give 9 + 20*2 => 49; but I can't come up with 47.

I had one of my students guess that two nines was ninety-one. He had no idea
where it came from either.


> They could not explain it either.

If you wrote the expression down, I can't explain it.

If you *spoke* it to them, the answer is easy: what you said and what they kept
in their short-term memory are different. For people who aren't used to doing
many numerical calculations in their head, everything except the "times two"
would be unfamiliar and therefore take more time and memory to process, which
takes away attention from listening to the rest of the expression.

I can completely believe that if you just fired off the expression rapidly:

"three squared plus root four hundred all by two"

or worse if you pronounced the brackets:

"open paren open paren three squared close paren plus the square root of four
hundred close paren by two"

they could have been calculating *anything* by the time you get to the end.


-- 
Steve
“Cheer up,” they said, “things could be worse.” So I cheered up, and sure
enough, things got worse.