📜  资质|算术能力4 |问题2

📅  最后修改于: 2021-05-13 21:46:15             🧑  作者: Mango

3,9,27,81……..531441中有多少个术语?

(A) 25
(B) 12
(C) 13
(D) 14答案: (B)
解释:

3, 9, 27, 81..............531441 form a G.P. 
with a = 3 and r = 9/3 = 3
Let the number of terms be n

根据公式,

GP的第N个项表示为T n = axr n-1

Then 3 x 3n-1 = 531441
∴ 3n = 312
∴ n = 12

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