$Late Christmas question...$

the # of gifts is = to the what day of Christmas the gift get?! So,

$1st = 1 gift$

$2nd = 1+2 gift$

$3rd = 1+2+3 gifts$

$4th = 1+2+3+4 gifts$

...

$12th = 1+2+3+4+...+12 gifts.$

Therefore, the total number of gifts is equal to:

Summation of $(1 + a_{n})(n/2)$ n= 1->12

= 1+1+2+1+2+3+...+1+2+3+4+...+12

= 12(1) + 11(2) + 10(3) + 9(4) + 8(5) + 7(6) + 6(7) + ... + 1(12)

= 2(12+22+30+36+40+42)

= 2(12+30+22+36+40+42)

= 2(42+58+82)

= 2(182)

= 364

$therefore,$

$364$ gifts all in all.. $(ans.)$