Math(s) problem - puzzle
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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?
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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.
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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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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.
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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
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!.
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"5 factorial" is not a solution; it is simply representing the answer (120) as a different equation. If you were set a problem in a mathematics test 300 - 0.5 x 150 and answered that it is 450 / 2, the teacher would be justified in marking it incomplete because it has not been reduced to the simplest terms.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.
My college math professor always told us to leave the simplification to the accountants, at least when it came to tests. No time for that. He was a great person. He later became the grad student ombudsman after putting up with us (rowdy undergrads) for three straight semesters! RIP
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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
Your answer is wrong, but not because of maths but because of your English usage. Your intention is to say the answer is 5 factorial in which case your first sentence would end with: "and announced that the answer was 5!." However, by leaving off the period, the exclamation mark ends the sentence, which means you are actually saying the answer is 5. I realize leaving off the period was deliberate to make the trick work, but it's inaccurate, and we are all engineers here :)
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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.
Yup, the scientific notation is far more often used (even wrote an Arduino "lib" for it). It has become handy in e.g. physics and the national debt :) Factorials, permutations and combinations are used a lot in (discrete) simulations e.g. for calculating chances of something happening. But it is true that people will often translate a chance of 1 in 100! as "will never happen" :)
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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
Much Ado About Nothing
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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
Nice trap.
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Yup, the scientific notation is far more often used (even wrote an Arduino "lib" for it). It has become handy in e.g. physics and the national debt :) Factorials, permutations and combinations are used a lot in (discrete) simulations e.g. for calculating chances of something happening. But it is true that people will often translate a chance of 1 in 100! as "will never happen" :)
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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
ooh, come to think of it your teacher might be referring to order of precedence for calculating algebra expressions. You might get the "correct" answer from him if you enforce your concept by expressing it something like (230 - 220) x 0.5, for this the answer is 5. Your teacher may have been implying that multiplication is calculated before subtraction, so he might be reading it as 230 - (220 x 0.5). It might be worth it to ask him if this is what he was thinking.
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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
Actually, your teacher realized you are more intelligent than him and he was embarrassed about that so he tried to cover for it by saying you were wrong. I wouldn't try to stick it to him or prove your correctness I would just let it go. There is really no point in upsetting the guy who gives you your final grade.
