Question 1090413
if it's two dimensional, then it's a simple matter of adding additional block for each level.
1,2,3,4,5,6,7,8,9,10,11,12
add them up and you get 78 total.


this is also an arithmetic series.


An = A1 + (n-1) * d


An is the nth term in the series.
A1 is the first term in the series.
n is the number of terms in the series.
d is the common difference.


in your series:
A1 = 1
An = 12
n = 12
d = 1


replace the variables in the formulas with their values and you get:
12 = 1 + 11 * 1 which becomes 12 = 12 which is true.
the formula is good.


there's a sum formula as well.
that formula is Sn = n * (A1 + An) / 2


replace the variables with the values that you know and you get:
Sn = 12 * (1 + 12) / 2 which becomes Sn = 12 * 13 / 2 which becomes Sn = 6 * 13 which becomes Sn = 78
formula is good as well since it agrees with the manual calculations.