freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-239-twenty-two-foolish-primes.english.md

---
id: 5900f45c1000cf542c50ff6e
challengeType: 5
title: 'Problem 239: Twenty-two Foolish Primes'
---

## Description
<section id='description'>
A set of disks numbered 1 through 100 are placed in a line in random order.

What is the probability that we have a partial derangement such that exactly 22 prime number discs are found away from their natural positions?
(Any number of non-prime disks may also be found in or out of their natural positions.)

Give your answer rounded to 12 places behind the decimal point in the form 0.abcdefghijkl.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler239()</code> should return 0.001887854841.
    testString: assert.strictEqual(euler239(), 0.001887854841, '<code>euler239()</code> should return 0.001887854841.');

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function euler239() {
  // Good luck!
  return true;
}

euler239();
```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>