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Understanding Math.random()


I am trying to understand the math logic behind Math.random().

For example, take this equation:

Math.floor(Math.random() * 6 ) +1

Now we will get a random number between 1-6, but WHY?

This is my understanding so far:

Math.random will generate a number between 0-1, but never 1. So, if we add Math.floor, that will round the number down. Then we multiply whatever number that is by 6 and add 1. I don't understand how this produces whole numbers between 1-6. Something is missing in my understanding!

Thanks! Liz

2 Answers

james south
.a{fill-rule:evenodd;}techdegree seal-36
james south
Front End Web Development Techdegree Graduate 33,271 Points

the first thing that happens is the random number, from 0 (inclusive) to 1 (exclusive), is generated and multiplied by 6. the result can be as low as 0 and as high as 5.99999999999. the next step is we take the floor of this, so we just drop any decimal part, so the result is a integer from 0 to 5, including 5. then we add 1, so now our range is 1 to 6, including 6.

Aha! That makes so much sense! Thank you!