This would seem to be a pretty simple calculation:
But many non-mathematicians stumble over it. The natural impulse is to start working from left to right:
– start with 9, subtract 3 to get 6
– divide 6 by 1/3 to get 18 (remember, dividing by a fraction is the same as multiplying by the reciprocal!)
– then add 1 to get 19.
If you got this, sorry, but it’s the wrong answer. Don’t feel too bad, since only 10% of viewers on Facebook got this problem right.
Working this way overlooks the fact that mathematics has a specific order of operations that takes precedence over the left-to-right approach. The mnemonic used is BODMAS: calculate functions in Brackets first, then do Orders (i.e. exponents and square roots), then DM for division and multiplication, and finally AS for addition and subtraction.
With this in mind, we can reconsider the equation. Since division and multiplication have to come first, we start by dividing 3 by 1/3 to get 9. Then do the addition and subtraction left to right: 9 – 9 yields 0, plus 1 for the correct final answer, 1.