2006-12-28 07:28:20 · 4 answers · asked by mazza 1 in Science & Mathematics ➔ Mathematics
un = 49
a1 = 1
r = 6
un = 1 + (n-1)r
49 = 1 + (n-1)6
49 = 1 + 6n - 6
49 - 1 + 6 = 6n
54 = 6n
n = 54 : 6
n = 9
Answer: There are nine terms. >><
2006-12-28 07:34:57 · answer #1 · answered by aeiou 7 · 2⤊ 0⤋
Without technical formulas, you can see that each gap is 6 (7-1, 13-7), while the total gap is 49-1=48.
48/6 = 8, so there are 8 gaps.
That means there are 8 terms after the first one, making 9 altogether.
2006-12-28 07:38:29 · answer #2 · answered by Hy 7 · 0⤊ 0⤋
nth term is 1st term plus (n-1) times common difference, so
49 = 1 + (n-1)6
48 = 6n - 6
54 = 6n
9 = n
2006-12-28 07:52:21 · answer #3 · answered by Philo 7 · 0⤊ 0⤋
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2006-12-28 07:53:21 · answer #4 · answered by Linda W 2 · 0⤊ 0⤋