Problem 51570. Count numbers whose reciprocals' decimal expansions terminate

Created by ChrisR

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<div style = "text-align: start; line-height: 20.4333px; min-height: 0px; white-space: normal; color: rgb(0, 0, 0); font-family: Menlo, Monaco, Consolas, monospace; font-style: normal; font-size: 14px; font-weight: 400; text-decoration: rgb(0, 0, 0); white-space: normal; "><div style="block-size: 63px; display: block; min-width: 0px; padding-block-start: 0px; padding-top: 0px; perspective-origin: 407px 31.5px; transform-origin: 407px 31.5px; vertical-align: baseline; "><div style="font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 31.5px; text-align: left; transform-origin: 384px 31.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 378.35px 7.91667px; transform-origin: 378.35px 7.91667px; unicode-bidi: normal; "><span style="">Some numbers (such as 4) have reciprocals with terminating decimal expansions, while others (such as 7) do not. Write a function that counts the numbers less than or equal to the input number whose reciprocals have terminating decimal expansions. For example, given 10, your function should return a count of 6, which corresponds to 1, 2, 4, 5, 8, and 10. </span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 14.1083px 7.91667px; transform-origin: 14.1083px 7.91667px; unicode-bidi: normal; "><span style="">         </span></span></div></div></div>

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23 Solutions
11 Solvers

Last Solution submitted on May 09, 2022

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Solution 5813543

3 Comments

3 Comments

Dyuman Joshi on 22 May 2021

Not sure why this fails, can anybody tell why?
Largest number in the test case is smaller than 1e16, this should work

ChrisR on 22 May 2021

Dyuman, your code misses a few powers of 2, for example, for the later tests.

Dyuman Joshi on 25 May 2021

Thanks, found the insufficiency of the method

Solution 5531265

1 Comment

1 Comment

ChrisR on 30 Apr 2021

Nikolaos, I don't think Cody scoring accounts for what you mentioned in the comment. :-)

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decimals number theory

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Problem 51570. Count numbers whose reciprocals' decimal expansions terminate

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Problem 51570. Count numbers whose reciprocals' decimal expansions terminate

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Last 200 Solutions

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Problem Recent Solvers11

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