---
id: 5900f3941000cf542c50fea7
title: 'Problem 40: Champernowne''s constant'
challengeType: 5
forumTopicId: 302066
dashedName: problem-40-champernownes-constant
---
# --description--
An irrational decimal fraction is created by concatenating the positive integers:
0.12345678910**1**112131415161718192021...
It can be seen that the 12th digit of the fractional part is 1.
If *dn* represents the *n*th digit of the fractional part, find the value of the following expression.
d1 × d10 × d100 × d1000 × d10000 × d100000 × d1000000
# --hints--
`champernownesConstant(100)` should return a number.
```js
assert(typeof champernownesConstant(100) === 'number');
```
`champernownesConstant(100)` should return 5.
```js
assert.strictEqual(champernownesConstant(100), 5);
```
`champernownesConstant(1000)` should return 15.
```js
assert.strictEqual(champernownesConstant(1000), 15);
```
`champernownesConstant(1000000)` should return 210.
```js
assert.strictEqual(champernownesConstant(1000000), 210);
```
# --seed--
## --seed-contents--
```js
function champernownesConstant(n) {
return true;
}
champernownesConstant(100);
```
# --solutions--
```js
function champernownesConstant(n) {
let fractionalPart = '';
for (let i = 0; fractionalPart.length <= n; i++) {
fractionalPart += i.toString();
}
let product = 1;
for (let i = 0; i < n.toString().length; i++) {
const index = 10 ** i;
product *= parseInt(fractionalPart[index], 10);
}
return product;
}
```