1) If Raenell was born in 1960, but has only had 10 birthdays on her birthday, how could she be 40 in the year 2000?
(Answer: Because 1960 was a Leap Year so Raenell must have been born on February 29.
Note: See how it is worded? "on her birthday" - we can only celebrate our birthday ON our birthday, in Leap Years.)

2) If Peter was born on February 29, 1956 and in 2004 turned 12 Leap Years on his birthday, how many years old is Peter?
(Answer: 48. The key is 12 Leap Years vs. how many "years" without the Leap, literally!)  

3) If Caroline was born February 29, 2000, how many birthdays will she celebrate, on her birthday, by 2008?
(Answer: 2)

4) If Jim was born February 29, 1976, how many times did he celebrate his birthday ON his birthday, by 2005?
(Answer: 7. Seven times four is 28. In 2005 Jim would be 29.)