Math Problems for children from 5 to 15 (2004) [pdf]

Re:Math Problems for children from 5 to 15 (2004) [pdf] by haxiomic on Monday July 19, 2021 @02:21PM (#27885718)

Works even if Kopecks are divisible: say the books value is 7.5, Mash must have 0.5 (7.5 - 7) and Misha 6.5 (7.5 - 1), however now when you combine them they sum to exactly 7.5 not less than, the only way to arrive at less than is if Masha has 0. So its always exactly 7

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Re:Math Problems for children from 5 to 15 (2004) [pdf] by gabagool on Monday July 19, 2021 @02:28PM (#27885792)

6.5 + 0.5 is 7.0, not 7.5, so that should be valid.

The book's cost can lie anywhere between [7, 8).

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Re:Math Problems for children from 5 to 15 (2004) [pdf] by haxiomic on Monday July 19, 2021 @02:53PM (#27886064)

Right on the original typo, but still not convinced, I’ve rephrased to original to try to be clearer

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Re:Math Problems for children from 5 to 15 (2004) [pdf] by thaumasiotes on Monday July 19, 2021 @03:01PM (#27886136)

> say the books value is 7.5, Mash must have 1.5 (7.5 - 7) and Misha 6.5 (7.5 - 1), however now when you combine them they sum to exactly 7.5 not less than

There are several problems with this:

- 7.5 - 7 is 0.5, not 1.5

- 1.5 + 6.5 is 8, not 7.5

- 0.5 + 6.5 is still less than 7.5

The problem specifies that 2x - 8 < x. There is no way to constrain this to the specific solution x = 7. Everything would work fine if the book cost -2.6 kopecks.

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Re:Math Problems for children from 5 to 15 (2004) [pdf] by haxiomic on Monday July 19, 2021 @03:12PM (#27886232)

Thank you :) I’m being very clueless today

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Re:Math Problems for children from 5 to 15 (2004) [pdf] by LeifCarrotson on Monday July 19, 2021 @02:28PM (#27885791)

6.5 plus 0.5 is 7.0, they don't add up to exactly 7.5.

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