Interview Question

Graduate Analyst Interview

-Leeds, England


There are three bags, one contains only red marbles, one contains only green marbles and the last contains both red and green. You do not know how many marbles are in each bag. Each of the bags is incorrectly labelled. How many times do you have to draw to figure out the correct labels of each bag?

AnswerAdd Tags

Interview Answers

5 Answers


One draw

Anonymous on


two draws max

Anonymous on


Draw one from each bag first (i.e. three in total) - two will be of the same colour. You could get red, green and green, for example. In that case, the bag you drew the red from is red only. Now you need to work out which of the other 2 bags is green only and which is mixed. So then you need to draw one from each of the 2 bags until you find a red - the one you draw the red from is the mixed bag. Therefore, the total number of draws you would need is unknown.

Anonymous on


You will need to draw one from each bag initially and then again one more time to confirm if each bag has the same colour marble in it as you may pick a red marble from a certain bag but it could be the one with mixed marbles in it

mohammed khaliq on


1 Draw. Solution: If all bags are labelled incorrectly, there's only two possibilities: (Using R=Red Bag, G=Green Bag, M=Mixed Bag) Actual Order: R G M Possible Labels: G M R or M R G (All other labelling makes one bag correctly labelled, can't be) Draw 1 marble from the bag labelled "M". If it's green, you've drawn from the green bag. If it's red, you've drawn from the red bag. Looking at the two possible labelling's, you can identify the other 2 bags.

Anony on

Add Answers or Comments

To comment on this, Sign In or Sign Up.