Double counting…if you select say A and B as the 2 women in your 8C2 and then in the 13C2 you add C and D. In another case you select C and B in the 8C2 and A and D in the 13C2. Yet another you select A and C in the 8C2 and B and D in 13C2. You are treating all as different cases. But they are one and the same.

The term “Double counting” in PnC doesn’t necessarily mean exactly double. It could be 3-4 times; we use “double counting” to indicate that some multiple counting type error is present.

In the example I took with AB and CD, we could also get AC and BD, AD and BC and so on; each case would be counted 6 times. (With 3 women each case would be counted thrice I think.)

Hi, What is wrong with this approach?

Step 1 : Select 2 women = 8C2

Step 2 : Select 4 from the remaining = 13C2

Answer=8C2*13C2

please help

Double counting…if you select say A and B as the 2 women in your 8C2 and then in the 13C2 you add C and D. In another case you select C and B in the 8C2 and A and D in the 13C2. Yet another you select A and C in the 8C2 and B and D in 13C2. You are treating all as different cases. But they are one and the same.

regards

J

Sir (8c2*13c4)/2 wats wrong in this soln?

The term “Double counting” in PnC doesn’t necessarily mean exactly double. It could be 3-4 times; we use “double counting” to indicate that some multiple counting type error is present.

In the example I took with AB and CD, we could also get AC and BD, AD and BC and so on; each case would be counted 6 times. (With 3 women each case would be counted thrice I think.)

regards

J