The array below represents a set of 16 playing cards, with the A's representing Aces:
A 5 5 A
5 2 4 10
3 8 7 4
A A 2 6
Divide the array into sections of adjacent cards so that the sum of the cards' values in each section will be 21. Each Ace can represent either 1 or 11 and you must determine how many sections are needed.
From Page-a-Day Calendar 2016: Amazing Mind Benders, by Puzzability (Mike Shenk, Amy Goldstein and Robert Leighton), Workman Publishing, NY; puzzle for August 6,7.
(In reply to re: Full solution - SPOILER
Once perceiving that each of the aces must be counted as 11, the solution was imminent and I did not bother to find out whether there are several solutions or just the one I've found.
Clearly, I did not look for others.
Edited on August 11, 2016, 10:47 am