Problem
COM-B1-M06-P002 Two Coins
#2
★☆☆☆☆ Level 1 of 5
There are \(9\) coins heads up. In one move, exactly two coins are flipped. Can all coins become tails up?
The parity of the number of heads is preserved.
The number of heads changes by \(-2\), \(0\), or \(2\), so its parity is preserved. It starts at \(9\) and would need to become \(0\). Odd cannot become even.
Basic coin problem.