# math

Find the number of term s in the following arithmetic sequence.
3, 9, 15, 21... 123

1. 👍 0
2. 👎 0
3. 👁 140
1. a = 3 , d = 6

term(n) = a + (n-1)d
123 = 3 + (n-1)(6)
120 = 6n - 6
126 = 6n
n = 126/6 = 21

there are 21 terms

1. 👍 0
2. 👎 0

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