When I say that the ORDER DOES NOT MATTER, I mean that there is no Specificied Order (in the question) in which we have to move. All the orders are important. And thus, we have to INCLUDE ALL THE ARRANGEMENTS.
If the question has just asked you to select one Red and one Blue ball, they haven't mentioned if the first ball is Red & second is Blue OR first ball is Blue & the second is Red.
Compare this with the question below in which the ORDER MATTERS:
There is a bag containing 6 Red balls and 4 Blue balls. Two balls are picked one after the other, without replacement. What is the probability that the first ball is Red and the second is Blue?
In this question the ORDER in which we have to go is specified, and thus MATTERS. We have to pick a Red Ball first and then a Blue Ball.
So, Answer:
P = (6/10)*(4/9)
We will not arrange in this case.
If the question has just asked you to select one Red and one Blue ball, they haven't mentioned if the first ball is Red & second is Blue OR first ball is Blue & the second is Red.
Compare this with the question below in which the ORDER MATTERS:
There is a bag containing 6 Red balls and 4 Blue balls. Two balls are picked one after the other, without replacement. What is the probability that the first ball is Red and the second is Blue?
In this question the ORDER in which we have to go is specified, and thus MATTERS. We have to pick a Red Ball first and then a Blue Ball.
So, Answer:
P = (6/10)*(4/9)
We will not arrange in this case.
Aneesh Bangia
GMAT Math Coach
[email protected]
GMATPad:
Facebook Page: https://www.facebook.com/GMATPad
GMAT Math Coach
[email protected]
GMATPad:
Facebook Page: https://www.facebook.com/GMATPad
