Multiple choice

Which term of the following series is 104? 4, 9, 14, 19, ...

  1. 19th

  2. 20th

  3. 21st

  4. 22nd
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C Correct answer
Explanation

This is an arithmetic progression with first term a = 4 and common difference d = 5. The formula for the n-th term is a + (n-1)d = 104. So, 4 + (n-1)5 = 104, which simplifies to (n-1)5 = 100, n-1 = 20, n = 21.

AI explanation

This sequence is an arithmetic progression with the first term equal to 4 and a common difference of 5. Using the nth term formula, a plus open parenthesis n minus 1 close parenthesis times d, we set 4 plus open parenthesis n minus 1 close parenthesis times 5 equal to 104. Solving this, 5 times open parenthesis n minus 1 close parenthesis equals 100, so n minus 1 equals 20, making n equal to 21, which is the 21st term.

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