Require help on simple maths question

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Bex55

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Hi! I am middle-aged and my maths lessons are a very distant memory! I have this calculation that I am not able to answer. I would very much appreciate help in this matter. Thank you in advance.
If 93 = 81 what does 85 equal?
 
Bex55 said:
Hi! I am middle-aged and my maths lessons are a very distant memory! I have this calculation that I am not able to answer. I would very much appreciate help in this matter. Thank you in advance.
If 93 = 81 what does 85 equal?
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Your problem - as posted - cannot be answered.

Do you have further context to the problem? Where did this problem come from? What other problems/topics that were being discussed along with this problem?
 
Bex55 said:
Hi! I am middle-aged and my maths lessons are a very distant memory! I have this calculation that I am not able to answer. I would very much appreciate help in this matter. Thank you in advance.
If 93 = 81 what does 85 equal?
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I would call this a puzzle or riddle, in which you need to guess an explanation for the "fact" shown. There is insufficient information given to conclude what is intended with anything close to certainty.

I see two immediate possibilities, because 81 is 9 squared ([MATH]9^2[/MATH]), which is [MATH]9^{3-1}[/MATH]; so the "rule" might be that "[MATH]ab = a^{b-1}[/MATH]"; or it could just as well be that "[MATH]ab = a\cdot b^2[/MATH]", so that "[MATH]93 = 9\cdot 3^2 = 9\cdot 9 = 81[/MATH]". These would give different results for "85".
 
Dr.Peterson said:
I would call this a puzzle or riddle, in which you need to guess an explanation for the "fact" shown. There is insufficient information given to conclude what is intended with anything close to certainty.

I see two immediate possibilities, because 81 is 9 squared ([MATH]9^2[/MATH]), which is [MATH]9^{3-1}[/MATH]; so the "rule" might be that "[MATH]ab = a^{b-1}[/MATH]"; or it could just as well be that "[MATH]ab = a\cdot b^2[/MATH]", so that "[MATH]93 = 9\cdot 3^2 = 9\cdot 9 = 81[/MATH]". These would give different results for "85".
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? Thank you Dr. Peterson
 
Bex55 said:
Hi! I am middle-aged and my maths lessons are a very distant memory! I have this calculation that I am not able to answer. I would very much appreciate help in this matter. Thank you in advance.
If 93 = 81 what does 85 equal?
Click to expand...
Seriously, if 93 = 81, then 85 can be whatever you want.
 
Bex55 said:
`it's relative, surely? 85 = 75, if 93= 81? Or am I horribly wrong?
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Nothing here is sure! One possibility is that they are just subtracting the same number (12) from any input, so 85 would be 73; or it could be proportional, which gives an ugly result; or it could be either of the ideas I suggested. Or anything else! There are infinitely many functions ("rules") that could turn 93 into 81.
 
Dr.Peterson said:
Nothing here is sure! One possibility is that they are just subtracting the same number (12) from any input, so 85 would be 73; or it could be proportional, which gives an ugly result; or it could be either of the ideas I suggested. Or anything else! There are infinitely many functions ("rules") that could turn 93 into 81.
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I think it is meant to be proportional? No worries.
 
You've told us nothing about the context of the riddle (it can't be called a math problem), on the basis of which I can assume anything about its intent.

But if you suppose it is a proportion, what answer do you get?
 
It is a basic rule of logic that if "P" is false then "if P then Q" if a true statement no matter what "Q" is! That is why Jomo can say "Seriously, if 93 = 81, then 85 can be whatever you want."
 
HallsofIvy said:
It is a basic rule of logic that if "P" is false then "if P then Q" if a true statement no matter what "Q" is! That is why Jomo can say "Seriously, if 93 = 81, then 85 can be whatever you want."
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Is that a necessary truth, or a convenient axiom? Serious question, not argumentative in spirit.
 
It is, as I said, a basic rule of logic. Personally I have always thought of it as "innocent until proven guilty"! Saying "if P then Q" tells us only what happens if P is true and nothing about what happens if P is false.
 
HallsofIvy said:
It is, as I said, a basic rule of logic. Personally I have always thought of it as "innocent until proven guilty"! Saying "if P then Q" tells us only what happens if P is true and nothing about what happens if P is false.
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I like Dr Peterson's answer that it is the more convenient axiom. We could always give a Scotch verdict of "not proven," but it does seem preferable to have a strict dichotomy. Anyway, thanks to both you and Fr.Peterson.
 
JeffM said:
I like Dr Peterson's answer that it is the more convenient axiom. We could always give a Scotch verdict of "not proven," but it does seem preferable to have a strict dichotomy. Anyway, thanks to both you and Fr.Peterson.
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I'd never heard of a "Scotch verdict", but it's in my dictionary. (I was expecting it to be a slur against the Scots, which includes a small part of me, so I was ready to take offense. Luckily I like to look things up first.)

I would have called it "three-valued logic".
 
Dr.Peterson said:
I'd never heard of a "Scotch verdict", but it's in my dictionary. (I was expecting it to be a slur against the Scots, which includes a small part of me, so I was ready to take offense. Luckily I like to look things up first.)

I would have called it "three-valued logic".
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Yes and no are easy to work with; maybe so, maybe not is a lot less helpful. Of course, it is the only answer available many times; life is far less clear cut than math.
 
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