Question 29
ProgressionsFind the sum of the first 21 terms of the progression −10, −8, −6, …
- A.180
- B.190
- C.200
- D.210
Show the answer and explanation
Answer: D (210)
Explanation
a = −10, d = 2, n = 21. S = 21/2 × (2(−10) + 20 × 2) = 21/2 × 20 = 210.
Find the sum of the first 21 terms of the progression −10, −8, −6, …
Answer: D (210)
a = −10, d = 2, n = 21. S = 21/2 × (2(−10) + 20 × 2) = 21/2 × 20 = 210.