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

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

Please, look at the picture?

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

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correct answer is 9 –  Aang Jun 28 '12 at 12:26
@avatar why you think so? can you proove your suggestion? –  Tural Aliyev Jun 28 '12 at 12:28
Why the hell I'm getting downvotes? –  Tural Aliyev Jun 28 '12 at 12:34
@Downvoters Why are you downvoting this post? –  Benja Jun 28 '12 at 12:35
@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. –  Henning Makholm Jun 28 '12 at 12:48
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marked as duplicate by Asaf Karagila, Qiaochu YuanJun 28 '12 at 12:34

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 $$\frac{a}{b(c+d)}.$$

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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 obtain different answers.

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