---
title: Count the coins
id: 59713bd26bdeb8a594fb9413
challengeType: 5
forumTopicId: 302238
---
## Description
There are four types of common coins in US currency:
quarters (25 cents)
dimes (10 cents)
nickels (5 cents), and
pennies (1 cent)
There are six ways to make change for 15 cents:
A dime and a nickel
A dime and 5 pennies
3 nickels
2 nickels and 5 pennies
A nickel and 10 pennies
15 pennies
## Instructions
Implement a function to determine how many ways there are to make change for a dollar using these common coins (1 dollar = 100 cents)
## Tests
```yml
tests:
- text: countCoins should be a function.
testString: assert(typeof countCoins === 'function');
- text: countCoins() should return 242.
testString: assert.equal(countCoins(), 242);
```
## Challenge Seed
```js
function countCoins() {
return true;
}
```
## Solution
```js
function countCoins() {
let t = 100;
const operands = [1, 5, 10, 25];
const targetsLength = t + 1;
const operandsLength = operands.length;
t = [1];
for (let a = 0; a < operandsLength; a++) {
for (let b = 1; b < targetsLength; b++) {
// initialise undefined target
t[b] = t[b] ? t[b] : 0;
// accumulate target + operand ways
t[b] += (b < operands[a]) ? 0 : t[b - operands[a]];
}
}
return t[targetsLength - 1];
}
```