Another of those Simple to State but Difficult to Answer puzzles, which should give you something to ponder over the festive period.
Over the twelve days of Christmas, who many gifts, in total, did my true love send to me?
That's it! Count the Partridge in a Pear Tree as one gift.
On the first day I receive one gift - a Partridge in a Pear Tree. On the second day I receive three gifts - two Turtle Doves and a Partridge in a Pear Tree. So this isn't 1+2+3 . . .+12
I receive twelve Partridges, one each day (12x1)
And I receive 22 Turtle Doves, two on each of eleven days (11x2)
And so on, until I receive twelve Drummers Drumming, all on the last day (1x12)
So we need to add 12, 22, 30, 36, 40, 42, 42, 40, 36, 30, 22 and 12, which equals 364.