what is the sum of the first four terms of geometric sequence where a1 = 16 and r = 2
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what is the sum of the first four terms of geometric sequence where a1 = 16 and r = 2
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240
a1 = 16
r = 2
n = 4
16 × 2 = 32
32 × 2 = 64
64 × 2 = 128
a1 = 16, a2 = 32, a3 = 64, a4 = 128
16 + 32 + 64 + 128 = 240
OR
Sn = a1 - a1r^n / 1 - r
S4 = 16 - 16 (2)^4 / 1 - 2
S4 = 16 - 16 (16) / -1
S4 = 16 - 256 / -1
S4 = -240 / -1
S4 = 240