Name: Layla
Who is asking: Other
Level of the question: All

Question: recently the solvable quandary of 5+5+5=550 came up (the question says that you have to put 1 straight line somewhere in the equation to make it true with out turning the "=" into a "not=" sign).

So two answers were put forward:
545+5=550 (the use of a line converting a + into a 4)
5+5+5(less than or equal to)550

There is currently an argument about the second solution. The disagreement is about whether this sign can be used. One person is arguing that the "less than or equal to" sign defines that the number on the left is in the range 550 and below. The other is saying that since the number (which is clearly defined with no variables) can never equal 550, then the "less than or equal to" sign cannot be used in this case.

Which one is the correct definition?



This is actually part of the broader issues about 'inclusive' definitions in mathematics.
So, for example, if I have more than $100,000, do I have more than $50,000? I think the answer is yes. Is a square also a rectangle? Mathematicians would say yes.

If a number A is less than B, is A less than or equal to B. The answer is yes. This is the way that mathematicians use the words 'or' and concepts.