From the given series, which are in Arithmetic Progression?
A. 7, 14, 21, 28, ...
B. 9, 17, 28, 40, ...
C. 3, 8, 13, 18, ...
D. 1, −1, −3, −5, ...
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, C and D only
A series is an arithmetic progression when the difference between any term and the one before it is the same all along (the common difference may be negative).
A. 7, 14, 21, 28, ... Correct. Each term is 7 more than the one before: common difference 7.
B. 9, 17, 28, 40, ... Incorrect. The differences are 8, 11 and 12, not the same, so it is not an AP.
C. 3, 8, 13, 18, ... Correct. Each term is 5 more than the one before: common difference 5.
D. 1, −1, −3, −5, ... Correct. Each term is 2 less than the one before: common difference −2.