 XP Math - Forums - View Single Post - Order of operations and variables
 View Single Post 09-24-2011   #7
MAS1   Join Date: Dec 2008
Posts: 249 Quote:
 Originally Posted by Mr. Hui You can do 144/4 or 4b first. The order does not change the answer.
I think this a case where a pair of parentheses can clear up a lot of confusion.

Mr. Hui is assuming that the above expression, as written, is equivalent to:

12^2 / (4b) + 4 so that when b = 9 the answer is 4. When he says it doesn't matter what order you evaluate 144/4 or 4b first he is assuming you would get either 144/4/9, or 144/36 which are the same.

However, others are assuming that the expression is equivalent to:

(12^2 / 4) x b + 4 which evaluates to 328.

As the expression is originally written I believe it has to be evaluated the second way so that the answer is 328.

12^2 / 4b + 4
144 / 4b + 4 Evaluate exponents
36 x b + 4 Evaluate division left to right
36 x 9 + 4 Substitution
324 + 4 Multiplication
328 Addition

The 4b term is what is confusing as we are used to treating it as a term in itself so that it seems like we have 144 / 36 when b = 9. 