Q:

How many children are there between P and Q in a row of children?
Statements:
I. P is fifteenth from the left in the row.
II. Q is exactly in the middle and there are ten children towards his right.

• 1
  I alone is sufficient while II alone is not sufficient
• 2
  II alone is sufficient while I alone is not sufficient
• 3
  Either I or II is sufficient
• 4
  Both I and II are sufficient