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Start your free trial###### Omar Farag

4,573 Points# JavaScript Random Number Generator

So I made this Random Number Generator in JS in which you can choose where your random number wants to be in-between. The thing is, it works with small numbers, but whenever I enter numbers bigger than 7, the random numbers are bigger than they are supposed to be.

## 3 Answers

###### Livia Dobai

21,894 PointsFor a random number between 1 and som top number should be:
`var dieRoll = Math.floor(Math.random() * topNumber) +1;`

and between two numbers:

`var dieRoll = Math.floor(Math.random() * (topNumber - bottomNumber + 1)) + bottomNumber;`

I suggest you that instead of num1 and num2 use more descriptive names for the variables...

###### Omar Farag

4,573 PointsLet me try that out.

###### Omar Farag

4,573 PointsIt works, but I don't understand what's happening. Would you mind explaining? Thanks.

###### Omar Farag

4,573 PointsHere's the code:

```
var num1 = prompt("Enter a starting number that you wan't your random number to be between");
var num2 = prompt("Enter and end number that you wan't your random number ro be between");
num1 = parseInt(num1);
num2 = parseInt(num2);
var dieRoll = Math.ceil(Math.random() * num2) + num1;
alert("You rolled a " + dieRoll);
```

###### Livia Dobai

21,894 PointsMath.random() returns a floating point random number between 0 and 1, not including 1 If you multiply the random result with a whole number we get a value between 0 and tha whole number -1

**Math.random() * 6 returns a floating pount number between 0 and 5**

If we want an integer az a value we can use the Math.floor() or Math.ceil() methods

**Math.floor(Math.random() * 6) returns a whole number between 0 and 5**

If we want a number between 0 and 6 we can add 1 to the result

**Math.floor(Math.random() * 6) + 1 returns a whole number between 0 and 6**

If we want the bottom number to be greater than 1 we must use the sequent formula: multiply the random number with (topNumber - bottomNumber +1) and add the the bottomNumber to it

**Math.floor(Math.random() * (topNumber - bottomNumber + 1)) + bottomNumber;**

You can see the whole explanation in this video lesson: https://teamtreehouse.com/library/javascript-basics/working-with-numbers/the-random-challenge-solution

Hope itβs more clear now...

## Livia Dobai

21,894 Points## Livia Dobai

21,894 PointsCan you please post your code?