The numbers 3, 10, 17, 24, 31, and 38 are the first six terms of an infinite seq

游客2024-01-12  21

问题 The numbers 3, 10, 17, 24, 31, and 38 are the first six terms of an infinite sequence in which each term after the first is 7 greater than the preceding term. What is the 45th term of the sequence?

选项 A、308
B、311
C、312
D、315
E、318

答案 B

解析 数字3,10,17,24,31和38是一个无穷数列(infinite sequence)的前六项,该数列的每一项都比前一项大7,问这个数列的第45项是多少?
解:本题的正确答案是(B)。由题意可知,该数列是一个等差数列,其首项a1=3,其公差为d=7,根据等差数列的通项公式可得:a45=a1+(n-1)d=3+(45-1)×7=311
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