Thread: Logic / maths

Understanding the problem.. or comprehending the issue.. Maths is maths.. but logic must prevail.. or not.

5+5+5-5+5+5-5+5x0= ? If you use your calculator you should get 0. Because anything multiplied by 0 is 0.

but... If you talk it through..

you get to 15 and then add the last ( 5x0 ) so I see some argument for the answer of this riddle being 15.

I will make it clear that billions of dollars have been lost because of silly little errors.. is this one ?

Originally Posted by astromark

Understanding the problem.. or comprehending the issue.. Maths is maths.. but logic must prevail.. or not.

5+5+5-5+5+5-5+5x0= ?

When writing down a problem such as this, you can use parenthesis to remove the possible ambiguity:

(5+5+5-5+5+5-5+5)x0= should indeed give you zero.

If you use a method, or a calculator, that calculates the total at each step, left to right, you'll get the same answer, zero.

However, by convention, multiplications are done before additions, when there are no parentheses. So

5+5+5-5+5+5-5+5x0= would become 5+5+5-5+5+5-5+(5x0) =

Additions, and subtractions, can be done in any order, without affecting the total.

So 5+5+5-5+5+5-5+(5x0)= will result in the same value as -5-5+5+5+5+5+5+(5x0)=

The solution is to write it down unambiguously. If you both are using the same order-of-operations, it will be.

Originally Posted by grapes

So 5+5+5-5+5+5-5+(5x0)= will result in the same value as -5-5+5+5+5+5+5+(5x0)=

The solution is to write it down unambiguously. If you both are using the same order-of-operations, it will be.

You can always use prefix or postfix notation

+ - + + - + + 5 5 5 5 5 5 5 x 5 0

or

5 5 + 5 + 5 - 5 + 5 + 5 - 5 0 x +

RPN FTW!


(And some more characters because that was "too short").

I type it into ambi and I get 5 somehow:

Ambi - an RPN programming language