# 6/2*(1+2) is 1 or 9? [duplicate]

Possible Duplicate:
What is 48÷2(9+3)?

Which calculator shows true result and how to prove achieved result?

• correct answer is 9 – Aang Jun 28 '12 at 12:26
• @avatar why you think so? can you proove your suggestion? – Tural Ali Jun 28 '12 at 12:28
• @BenjaLim: Apparently there was a period some time (more than a year) ago when the site was overwhelmed with variants of this question. Seeing it again must have been a traumatic experience for someone. – hmakholm left over Monica Jun 28 '12 at 12:48
• The Casio fx-570MS to the left is a model from 2005, whereas Casio fx-50FH was introduced in 2008, so I would go with the newer calculator on the right. Which, incidentally, has the right answer. – Per Manne Jun 28 '12 at 13:08
• I have given an answer here which explains why calculators give different results. The question to which it has been originally linked to is somewhat too broad. math.stackexchange.com/a/2356210/54967 – noir1993 Jul 12 '17 at 14:20

Despite every personal belief, a notation like $a/b(c+d)$ is ambiguous. At school I learned that this should be $$\frac{a}{b}(c+d),$$ but even in research papers somebody could read $$\frac{a}{b(c+d)}.$$

when two operations have same precedence, then the operations are done from left to right.So here, division is done first and then multiplication.This is just a convention.Without this, this expression is ambiguous.

The reason why calculators are giving different results is because one is calculating,

$$\frac{6}{2\cdot(2+1)} = 1$$

while the other is calculating,

$$\frac{6}{2}\cdot(2+1) = 9$$

Depending on what you want to calculate, you could obtain different answers.