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Math Problems @MathQuizzes

Short math problems, mind training, science quizzes. Joined June 2014
  • Tweets
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  • Followers
    496
  • Following
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Math Problems @MathQuizzes

12 years ago

I have 11 coins on a board, all tales up. In a step, I can turn exactly 5 coins. Can I have all heads up in 7 steps? And in 6 steps?

MathQuizzes Profile Picture

Math Problems @MathQuizzes

12 years ago

Can I cut up a symmetric octogon into parallelogramms of equal area?

MathQuizzes Profile Picture

Math Problems @MathQuizzes

12 years ago

If n+1<k<2n, can n number of lines divide a plane into k subplanes?

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Math Problems @MathQuizzes

12 years ago

@GraemeMcRae Ahh! I see the problem here. I did my proof for odd numbers, not even numbers. Oh, snap, stupid me. You are right.

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Math Problems @MathQuizzes

12 years ago

Find a factorization for 4x^3 - 11x - 3

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Math Problems @MathQuizzes

12 years ago

@GraemeMcRae Leading zeros are not allowed in the first hand, because zero is not an even number.

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Math Problems @MathQuizzes

12 years ago

@GraemeMcRae That is a widely known riddle :)

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Math Problems @MathQuizzes

12 years ago

Given 2 ropes, known that both of them burn down exactly in 1 hr. How can you measure exactly 15 min by burning the ropes? (Don't fold them)

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Math Problems @MathQuizzes

12 years ago

I have two bottles, a 3L and an 5L one. I have infinite water. How can I measure out exactly 4L water with these?

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Math Problems @MathQuizzes

12 years ago

@Derektionary The original problem uses an equal-arm balance, but that did not fit into a tweet. For a modern balance, your solution is good

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Math Problems @MathQuizzes

12 years ago

@GraemeMcRae It's 8*3^74, but still impressive. The proof I got for it uses a recursive series for the n-digit numbers, like you started.

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Math Problems @MathQuizzes

12 years ago

@Derektionary this is better, but I'm looking for the minimum amout of measurements. It's not this easy :)

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Math Problems @MathQuizzes

12 years ago

@SteveDataCrunch The best explanation for domains I can find at the moment: bit.ly/1nug1tx

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Math Problems @MathQuizzes

12 years ago

@Derektionary So if the particular coin you weighted has the expected mass, how do you point out the 'wrong' one from the other n-1?

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Math Problems @MathQuizzes

12 years ago

@SteveDataCrunch Nop, the domain is stricter than that. There is an inital value, which sort of forces you for an interval as the domain.

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Math Problems @MathQuizzes

12 years ago

@Derektionary Oh, lad, I'm sorry. You are right. It was me who was missing a minus sign :)

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Math Problems @MathQuizzes

12 years ago

@MathQuizzes Also a domain for the solution would be nice.

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Math Problems @MathQuizzes

12 years ago

@Derektionary Almost got it rifgt, but its a plus, not a minus in the denominator.

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Math Problems @MathQuizzes

12 years ago

I've got n coins, one of them is heavier, others are the same. I have a balance. How many measures do I have to take to find the odd one?

MathQuizzes Profile Picture

Math Problems @MathQuizzes

12 years ago

@Derektionary No, we can't say that.

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