Problem 19 · 2013 Math Kangaroo
Medium
Logic & Word Problems
caseworkwork-backward
Andi, Berti, Christa, Doris and Edi were born on these days: 20.02.2000, 12.03.2000, 20.03.2000, 12.04.2000 and 23.04.2000 (in some order). Andi and Edi have their birthday in the same month. Berti and Christa also share a birthday month. Andi and Christa were born on the same day of different months. Doris and Edi were also born on the same day of different months. Which of these children is the youngest?
Show answer
Answer: B — Berti
Show hints
Hint 1 of 2
Match the four clues to the five dates; same-month and same-day pairs are very restrictive.
Still stuck? Show hint 2 →
Hint 2 of 2
Once everyone has a date, the youngest is simply the latest one.
Show solution
Approach: deduce the date assignment
- Same-month pairs force Andi&Edi into one of the doubled months and Berti&Christa into the other.
- Same-day clues then fix Andi = 12.03, Christa = 12.04, Edi = 20.03, Doris = 20.02, Berti = 23.04.
- The latest date, 23.04.2000, belongs to Berti.
- So Berti is the youngest.
Mark:
· log in to save