60 lines
1.2 KiB
Markdown
60 lines
1.2 KiB
Markdown
---
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id: 5900f3b31000cf542c50fec6
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challengeType: 5
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title: 'Problem 71: Ordered fractions'
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---
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## Description
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<section id='description'>
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Consider the fraction, n/d, where n and d are positive integers. If n<d and HCF(n,d)=1, it is called a reduced proper fraction.
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If we list the set of reduced proper fractions for d ≤ 8 in ascending order of size, we get:
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1/8, 1/7, 1/6, 1/5, 1/4, 2/7, 1/3, 3/8, 2/5, 3/7, 1/2, 4/7, 3/5, 5/8, 2/3, 5/7, 3/4, 4/5, 5/6, 6/7, 7/8
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It can be seen that 2/5 is the fraction immediately to the left of 3/7.
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By listing the set of reduced proper fractions for d ≤ 1,000,000 in ascending order of size, find the numerator of the fraction immediately to the left of 3/7.
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>euler71()</code> should return 428570.
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testString: assert.strictEqual(euler71(), 428570, '<code>euler71()</code> should return 428570.');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function euler71() {
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// Good luck!
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return true;
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}
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euler71();
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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