Math(s) problem - puzzle
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My teacher asked me to write a program on the board and solve it. I wrote:
230 - 220 x 0.5
and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.
Brent
The teacher was not embarrassed but shocked that any student could be so wrong. The division MUST be carried out before the subtraction. 230 – 220 × 0.5 = 230 – 110 = 120. Try it in any scientific calculator or programming language. You are alone (I hope) in thinking the answer is 5. Are you perhaps joking?
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You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
You write "the answer to which is obviously not 5". Nobody ever said that. The OP sais that he "announced that the answer was 5!". Do you see the difference? The exclamation mark. The answer is 5! (five factorial) and 5!=5*4*3*2*1=120 so 5! is the correct answer :-)
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Yeah, you're both on the AR page. :-D
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Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
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You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
In the UK they teach BODMAS as the order of precedence Brackets Operations Division MMultiplication AAddition SSubtraction see Order of operations - Year 6 - P7 - Maths - Home Learning with BBC Bitesize - BBC Bitesize[^]
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You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
In the UK they teach BODMAS as the order of precedence Brackets Operations Division MMultiplication AAddition SSubtraction see Order of operations - Year 6 - P7 - Maths - Home Learning with BBC Bitesize - BBC Bitesize[^]
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In the UK they teach BODMAS as the order of precedence Brackets Operations Division MMultiplication AAddition SSubtraction see Order of operations - Year 6 - P7 - Maths - Home Learning with BBC Bitesize - BBC Bitesize[^]
Please don't repost if your comment does not appear immediately: both of these went to moderation and required a human being to review them for publication. In order to prevent you being kicked off as a spammer, both had to be accepted, and then I have to clean up the spares. Have a little patience, please! I've deleted the other version.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!
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My teacher asked me to write a program on the board and solve it. I wrote:
230 - 220 x 0.5
and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.
Brent
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A statisticus / mathematician will provide answers as factorial as often numbers are too big to write down. E.g. 5! is quite easy but 7000000000! is huge. Assuming the world population is 7000000000, 7000000000! is approximately the number of ways you can put their names in a list. As there are people with the same name the number is actually less but still huge. There are even statistic problems where numbers like n!! (n factorial factorial *) are used which can be even "bigger than huge". *) besides "n factorial factorial", there exist "n double factorial" which is n x (n-2) x (n-4) ... x 1)
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3! - 1 I think you'll find :) It's curious - nearly everyone I know was taught BODMAS - its the same as PEDMAS, but B=Brackets, O="of". PEDMAS is probably better. Also the great Indian chief "SOH-CAH-TOA". I wonder if they still teach the latter in schools.
KeithBarrow.net[^] - It might not be very good, but at least it is free!
Rather than the Indian chief, we were taught the great Welsh anthem: Sons of Harlech Come and Harken To our Anthem A geographic thing, I suppose. We were 50 miles from Wales but several thousand from the Indians.
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You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
Note that he said "5!", not "5".
He might have given it away too big a clue if he had ended his sentence properly with a period like "...I said the answer is 5!."
Good nerdy riddle. -
If you solve it left-to-right, ignoring precedence order, then the answer is 5. An old TI calculator would give you that answer. Today's windows calculator will not: it says 120 because the multiplication is done first.
"They have a consciousness, they have a life, they have a soul! Damn you! Let the rabbits wear glasses! Save our brothers! Can I get an amen?"
"5!" = 120
It's a clever nerdy riddle. I like it!
I wonder if I'd have been hassled after math class for giving such an answer? and I just noticed that Microsoft Excel doesn't recognize factorials. -
And today you learn that nobody likes a smartarse ... :laugh:
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!
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The teacher was not embarrassed but shocked that any student could be so wrong. The division MUST be carried out before the subtraction. 230 – 220 × 0.5 = 230 – 110 = 120. Try it in any scientific calculator or programming language. You are alone (I hope) in thinking the answer is 5. Are you perhaps joking?
-
You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
-
My teacher asked me to write a program on the board and solve it. I wrote:
230 - 220 x 0.5
and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.
Brent
-
You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
-
My teacher asked me to write a program on the board and solve it. I wrote:
230 - 220 x 0.5
and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.
Brent
Oh, come on! I immediately saw that: 5!=120
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More likely New Orleans!
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A statisticus / mathematician will provide answers as factorial as often numbers are too big to write down. E.g. 5! is quite easy but 7000000000! is huge. Assuming the world population is 7000000000, 7000000000! is approximately the number of ways you can put their names in a list. As there are people with the same name the number is actually less but still huge. There are even statistic problems where numbers like n!! (n factorial factorial *) are used which can be even "bigger than huge". *) besides "n factorial factorial", there exist "n double factorial" which is n x (n-2) x (n-4) ... x 1)
Interesting. Never knew that anyone ever used factorials other than as, shall I say, a "mathematically interesting" thing and then moving on. When it comes to extremely large (or small) numbers, I always understood that the standard was to use powers of 10, for example, googling for the weight of the earth, the result is expressed as 5.972x10^24 kg.
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My teacher asked me to write a program on the board and solve it. I wrote:
230 - 220 x 0.5
and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.
Brent
Is it because you are saying 5! (factorial). 230 - 220 x 0.5 = 230 - 110 = 120 which is == 5x4x3x2x1 or 5!.
