freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-235-an-arithmetic-geometric-sequence.md

---
id: 5900f4571000cf542c50ff6a
title: 'Problem 235: An Arithmetic Geometric sequence'
challengeType: 5
forumTopicId: 301879
dashedName: problem-235-an-arithmetic-geometric-sequence
---

# --description--

Given is the arithmetic-geometric sequence u(k) = (900-3k)rk-1.

Let s(n) = Σk=1...nu(k).

Find the value of r for which s(5000) = -600,000,000,000.

Give your answer rounded to 12 places behind the decimal point.

# --hints--

`euler235()` should return 1.002322108633.

```js
assert.strictEqual(euler235(), 1.002322108633);
```

# --seed--

## --seed-contents--

```js
function euler235() {

  return true;
}

euler235();
```

# --solutions--

```js
// solution required
```