There are 7 books on a shelf, of which 2 are paperbacks and 5 are hardbacks. How many possible selections of 4 books from this shelf include at least one paperback?	Pick one
A) a) 30	B) b) 45	C) c) 50	D) d) 55	E) e) 60
approach 1   at-least 1 paper back = total - no paper back   7c4-5c4 = 30   approach 2   at-least 1 paper back = 1 paper back , 3 hard back or 2 paper back 2 hard back   = 2c1*5c3+2c2*5c2 = 30   a) 30nswer is a) 30
<result>A</result>
There are 7 books on a shelf, of which 2 are paperbacks and 5 are hardbacks. How many possible selections of 4 books from this shelf include at least one paperback?