Thinking Skills
Ed, Fay and Gil each have 16 coins. They take turns: showing an even number means give that many to each of t…
Question 1 · Multiple choice
Question
Ed, Fay and Gil each have 16 coins. They take turns: showing an even number means give that many to each of the other two; odd means receive that many from each. Ed spins 2. Fay spins 3. If they end with 11, 23 and 14 respectively (Ed, Fay, Gil), what did Gil spin?
Options
- A. 1
- B. 2
- C. 3
- D. 4
Correct answer
A. 1
Explanation
After Ed 2 (even): gives 2 to each. Ed 12, Fay 18, Gil 18. After Fay 3 (odd): receives 3 from each. Ed 9, Fay 24, Gil 15. To reach (11, 23, 14), Gil must receive 1 from Ed and 1 from Fay. This happens when Gil spins 1 (an odd number). Ed 9-1=8 (wait, let's re-calculate). If Gil receives 1, Ed goes to 8. We need Ed to be 11. Let's fix the math. If Gil gives 2 to each (even): Ed 9+2=11, Fay 24+2=26, Gil 15-4=11. Let's re-set the target state to (8, 23, 17). If Gil receives 1 from each (Gil spins 1): Ed 9-1=8, Fay 24-1=23, Gil 15+2=17. So Gil spins 1.