Apologies for not posting the solution last weekend, I was traveling outside the country.

I received an overwhelming number of correct solutions for this puzzle. First one to come back was Alok Kucklous. Others were Aman Singla, Girish Tutakne, Ashutosh Diwakar and Akash Tayal. Special mentions for two children – Damini Rana and Ishir Gupta – for sending the correct answers – well done!

The answer is that stacks cannot be made equal. I Am taking the liberty of copying Akash Tayal’s explanation.

The stacks cannot be made equal because each time we add 2 coins, the total number of coins remains odd (since it starts at 21).  To make the stacks equal, the sum is even (because there are an even number of stacks).

Hope you enjoyed the puzzle!