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

Please, look at the picture?

http://s16.radikal.ru/i190/1206/3b/7411739c6d9a.jpg

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

3 Answers 3

7

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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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.

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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 could obtain different answers.