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Start your free trial###### Łukasz Giergielewicz

4,059 Points# Why not use Math.ceil()?

```
var randomNumber = Math.ceil(Math.random() * 6);
```

Seems to only return values between 1 and 6, is there a possibility of a failure?

## 2 Answers

###### Steven Parker

225,769 PointsWhile it's highly unlikely, Math.random() can theoretically return zero, so your formula would return 1-6 with approximately equal likelihood, but perhaps also 0 with a far lower probability.

That's why Math.floor() is generally used instead of Math.ceil() with random formulae, since the result can be relied on to remain in the range and give each value approximately equal probability.

###### Doron Geyer

**Full Stack JavaScript**Techdegree Student 13,896 Points

What Steven has said above in simpler terms.

Going to break it down into steps.

`Math.random();`

provides values from 0(including zero) to 0.99999999999 but never 1.

`Math.floor`

will round it down to the nearest whole number.

so if we take it mathematically. even if you get 0.9999999 as above and you * 6 you will get 5.999999 which`Math.floor`

will drop to 5

so your range is 0-5 the "+1" just increases the minimum from 0 to 1 and the max from 5 to 6.

with `Math.ceil`

if you random 0 it will leave the value as zero.

which will mean that your code
`var randomNumber = Math.ceil(Math.random() * 6);`

gives you a range of 0 to 6 instead of 1 to 6 like a dice.