Tell us what’s happening:
One of the test is erroneous :
“multiplesOf3and5(1000)` should return 233168”
But that’s in fact the result for 999 !
The correct answer is 234168…

**Your code so far**

function multiplesOf3and5(number) {
const mul15 = Math.floor(number / 15);
const res15 = number % 15;
let res;
if (res15 < 7) {
if (res15 < 5) res = 3 + mul15 * 15;
else if (res15 == 5) res = 8 + mul15 * 30;
else res = 14 + mul15 * 45;
}
else {
if (res15 < 10) res = 23 + mul15 * 60;
else if (res15 < 12) res = 33 + mul15 * 75;
else res = 45 + mul15 * 90;
}
return res + mul15 * 60 + 105 * mul15 * (mul15 - 1) / 2;
}
console.log(multiplesOf3and5(10));

**Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.85 Safari/537.36.