---
title: Large sum
---
## Problem 13: Large sum
Challenge: Work out the first ten digits of the sum of one-hundred 50-digit numbers.
## Spoiler Alert!
## One Solution:
```
function largeSum(arr) {
let sum = arr.reduce((acc, item) => acc + Number(item), 0); // 8.348422521139211e+49
let str = sum.toString().split('e')[0]; // '8.348422521139211'
return 1e+9 * str.slice(0,11); // 8348422521
}
const testNums = [
'37107287533902102798797998220837590246510135740250',
'46376937677490009712648124896970078050417018260538'
];
largeSum(testNums);
```
### Code Explanation:
* The function receives an array of strings
* The first line converts the strings to numbers and adds them
* The second line converts the large sum to a string with toString, then gets everything to the left of 'e' using String.split().
* The third line multiplies 1,000,000,000 by the first 11 characters to implicitly coerce the string to a 10 digit number
* Note: One regular expression could accomplish the same task as the second and third lines together
### Resources
* Array.reduce()
* String.split()