---
id: 5900f3b41000cf542c50fec7
challengeType: 5
title: 'Problem 72: Counting fractions'
forumTopicId: 302185
---
## Description
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.
If we list the set of reduced proper fractions for d ≤ 8 in ascending order of size, we get:
It can be seen that there are 21 elements in this set.
How many elements would be contained in the set of reduced proper fractions for d ≤ 1,000,000?
## Instructions
## Tests
```yml
tests:
- text: countingFractions() should return a number.
testString: assert(typeof countingFractions() === 'number');
- text: countingFractions() should return 303963552391.
testString: assert.strictEqual(countingFractions(), 303963552391);
```
## Challenge Seed
```js
function countingFractions() {
return true;
}
countingFractions();
```