The first term of a series is 8 and the common difference is 2. i. the series is 8 + 10 + 12 + ........ ii. its 10th term = 26 iii. the sum of its first 15 terms = 300

Rajshahi Board 2025

The first term of a series is 8 and the common difference is 2.

Think it through first, then pick an option.

Answer and explanation

Correct answer: a i and ii

i and ii are true: the series is 8 + 10 + 12 + ... and the 10th term is 8 + 9 × 2 = 26; iii is false since the sum is 330.

Why the other options are wrong

b i and iii: iii is false: S₁₅ = (15/2){16 + 14 × 2} = 330, not 300; ii is left out though the 10th term is 26.
c ii and iii: iii is false (the sum is 330) and i is left out, though the series is 8 + 10 + 12 + ....
d i, ii and iii: iii is false: the sum of 15 terms is 330, so all three cannot be true.