The formula for the sum of a geometric series is:
S = a(1 - r^n) / (1 - r)
where S is the sum of the series, a is the first term, r is the common ratio, and n is the number of terms.
Using this formula, we can find the sum of the series where a1 = 11 and r = 3 for 7 terms:
S7 = 11(1 - 3^7) / (1 - 3)
S7 = 11(-2,186) / (-2)
S7 = 11 x 1,093
S7 = 12,023
Therefore, the sum of the geometric series where a1 = 11 and r = 3 for 7 terms is 12,023.