Which of the following list of numbers is/are an Arithmetic Progression?
(A) −2, 2, −2, 2, −2, ...
(B) 1, −1, −3, −5, ...
(C) 21, 18, 15, ...
(D) 20, 17, 14, 11, ...
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B), (C) and (D) only
A list of numbers is an arithmetic progression (AP) when each term is obtained by adding the same fixed number (the common difference) to the term before it.
(A) −2, 2, −2, 2, −2, ... Incorrect. The differences are \(+4\), \(-4\), \(+4\), ...; they keep changing sign, so there is no common difference.
(B) 1, −1, −3, −5, ... Correct. Each term is 2 less than the one before: common difference \(-2\).
(C) 21, 18, 15, ... Correct. Each term is 3 less than the one before: common difference \(-3\).
(D) 20, 17, 14, 11, ... Correct. Each term is 3 less than the one before: common difference \(-3\).