Given a random number generator, using it to make a new one

Question

Given a function F that generates random numbers between 1 and 5, how would I write a function G, using F, to generate random numbers between 1 and 7?

The probability of each number generated by G should be the same.

So far, I have tried the equation G=F + (5*(F/7)), although I'm not sure that all of the probabilities are the same.

wanted to know if its the correct solution ... guess its not ... above is not equal probability ... found this ... http://stackoverflow.com/questions/137783/expand-a-random-range-from-15-to-17?rq=1 — Lav, Feb 16 '13 at 03:26

score 0 · Answer 1 · answered Feb 20 '13 at 09:33

Pseudocode:

function g()
    repeat
        // result will be equidistributed in 0..24
        result = (f()-1)*5 + (f()-1);
        // wait till we have something below 21, on average this happens 21 out of 25 times in the first pass
        if (result < 21): return 1 + (result % 7)

Given a random number generator, using it to make a new one

1 Answers1