Wednesday, May 18, 2011

Arithmetic fail

My sister-in-law asked me to clarify this simple arithmetic expression.

The question is, do they mean

Or, do they mean

In the absence of brackets to clarify, mathematical convention would suggest that option (1) is the correct interpretation since the division symbol pertains to the first operand on its right. In our case, it's a 2. If they had intended option (2), then they would have to enclose 2(9+3) all in brackets, as in

The problem is we don't know the mathematical sophistication of the person who came up with the question. How many times have I seen a "skill testing question" that looks something like this...

Following standard mathematical convention, my answer would be 16.166666... But, somehow that's less satisfying than the unconventional answer of 3.

1 comment:

  1. Funny - I immediately read it as 24*12 but then second guessed myself because I've never seen a skill testing question that resulted in an answer of 288. I'm sure the answer they're anticipating is 2, but that's objectively wrong. If there's both a multiplication and a division operation outside of parentheses, you're supposed to work left to right.