If everyone submits, maybe one of us will win the NPR Sunday Puzzle:
This Week’s Challenge from the Grabarchuk family: Take 15 coins. Arrange them in an equilateral triangle with one coin at the top, two coins touching below, three coins below that, then four, then five. Remove the three coins at the corners so you’re left with 12 coins. Using the centers of the 12 coins as points, how many equilateral triangles can you find by joining points with lines?
If you know the answer to next week’s challenge, submit it here. Listeners who submit correct answers win a chance to play the on-air puzzle. Important: Include a phone number where we can reach you Thursday at 3 p.m. Eastern.