Multiple choice

The 20th term from the last of arithmetic sequence 5, 10, 15, 20..... 150 will be

  1. $25$
  2. $45$
  3. $55$
  4. $85$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sequence: 5, 10, 15, ..., 150. This is an AP with a=5, d=5. Number of terms = 150/5 = 30. 20th term from the last is (30 - 20 + 1) = 11th term from the beginning. a11 = a + 10d = 5 + 10(5) = 55.

AI explanation

To find the nth term from the end of an arithmetic sequence, use the formula $a_n = l - (n-1)d$, where $l$ is the last term and $d$ is the common difference. Substituting the given values gives the 20th term from the end as $150 - (20-1)5$. This calculates to $150 - 95$, which equals 55. The result is 55.

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