Are you sure you want to leave?

Your test is still in progress. If you leave this page or go back now, all your attempt wil not be saved.

Sandra has a bag of marbles containing red, blue and yellow marbles. The probability of Sandra picking out a red marble is 20%, and the probability of her choosing a blue one is three times the probability of her choosing a yellow one.

What is the minimum number of marbles in the bag?