3 thoughts on “CAT 15 Lead-up – 5

  1. sir in the last question ,we know that at least 1 doctor is selected by 2^8 – 1 ways and since only 7 doctors are remaining so shouldn’t it be ( 2^8 – (1+7C1) ways ?

    • Why do you feel seven are remaining? The two cases are separate. When we say none is selected, we mean none of the 8 (i.e. 8C0). When we say exactly 1, it also means 1 out of the 8 (i.e. 8C1). In this case, we want “at least 2” which means we need to remove the cases of “none” and “exactly 1” from all the 8 available. Which is what we have done here.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s