JavaScript: Print 3 random integers between 100 and 999 which is divisible by 5

Question

I don't know how to make the random numbers print only the ones that are divisible by 5

PS: I am a newbie

const min = 100;
const max = 999;

const a = Math.floor(Math.random() * (max - min + 1)) + min;
const b = Math.floor(Math.random() * (max - min + 1)) + min;
const c = Math.floor(Math.random() * (max - min + 1)) + min;

console.log(`${a} ${b} ${c}`);

// Sample output should be: 145 570 865

you can use remainder https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Remainder operator — SuleymanSah, Oct 26 '22 at 14:26
Does this answer your question? [What does % do in JavaScript?](https://stackoverflow.com/questions/8900652/what-does-do-in-javascript) — SuleymanSah, Oct 26 '22 at 14:27
You can use the Remainder (`%`) operator to detect whether a number is divisible by another number. But you'd be wiser to only select from a list of values that has already been restricted to valid values that are divisible by 5. Otherwise you'll be doing a lot of extra iterating while you wait for your random number generator to give you something divisible by 5. — Marc, Oct 26 '22 at 14:29
Does this answer your question? https://stackoverflow.com/questions/50560493/javascript-generating-a-random-number-that-can-be-divided-by-5 — Reyno, Oct 26 '22 at 14:29

score 3 · Answer 1 · answered Oct 26 '22 at 14:25

3

Think about it. To make sure your numbers are divisible by 5, how about generating random numbers from range 5 times smaller and then multiply by 5?

Like if I wanted to generate 0, 5, 10, 15 or 20, I could randomly pick [0..4] and then multiply the result by 5. Voilà!

answered Oct 26 '22 at 14:25

Robo Robok

21,132
17
68
126

so generate a number between `21` and `199` (including boundries ) and multiply it with 5, thats what I assume you are trying to say? because 21 * 5 = 105, and 199 * 5 = 995 – Ace Oct 26 '22 at 14:32
1

@Yan between 20 and 199. – Robo Robok Oct 26 '22 at 14:33
ok, I did not notice 100 was included – Ace Oct 26 '22 at 14:34

QueueHammer · Answer 2 · 2022-10-26T14:47:31.180

The easiest way to get your first requirement is to multiple some number by your divisor (like @Robo Robok said)

input * 5 = number devisable by 5

the next step is to bound your candidate numbers, you have an upper bound and a lower bound and they may not divide evenly so you'll have to round up and down

upper bound = floor(upper bound / 5)
lower bound = ceiling(lower bound / 5)

That range is what you want to use with your random number

number range = upper bound - lower bound

So, if we take the range and multiply it by the random number and multipy it by 5 you have your generator.

random number = (ceil(number range * random number)+lower bound) * 5

Because this was a JavaScript question:

rangedRandFactory = (multiple, min, max) => {
  const ceil = Math.floor(max/multiple);
  const floor = Math.ceil(min/multiple);
  const range = ceil - floor;
  return () => ((Math.ceil(range*Math.random()))+floor) * multiple
}

JavaScript: Print 3 random integers between 100 and 999 which is divisible by 5

2 Answers2