Each of the integers from 0 to 8, inclusive, is written on a separate slip of blank paper and the ten slips are dropped into hat. If the slips are then drawn one at a time without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10? Pick one:
A) 8
B) 9
C) 7
D) 6
E) 5
You should consider the worst case scenario: if you pick numbers 0, 1, 2, 3, 4 and 5 then no two numbers out of these 6 add up to 10.   Now, the next, 7th number whatever it'll be (6,7, or 8) will guarantee that two number WILL add up to 10. So, 7 slips must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10   Answer: 7
<result>C</result>
Each of the integers from 0 to 8, inclusive, is written on a separate slip of blank paper and the ten slips are dropped into hat. If the slips are then drawn one at a time without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10?