Multiple choice

How many terms are there in the arithmetic sequence 15, 20, 25, 30, \dots, 145?

  1. 22

  2. 25

  3. 24

  4. 26

  5. 27
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E Correct answer
Explanation

This is an arithmetic progression with first term a = 15 and common difference d = 5. The nth term formula is an = a + (n-1)d. Setting 145 = 15 + (n-1)5 gives 130 = 5(n-1), so n-1 = 26 and n = 27. There are 27 terms from 15 to 145 inclusive.

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