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Question
The sum of first 16 terms of the AP: 10, 6, 2,... is ______.
Options
–320
320
–352
–400
Solution
The sum of first 16 terms of the AP: 10, 6, 2,... is –320.
Explanation:
Given, AP is 10, 6, 2,...
Here,
First term a = 10,
Common difference,
d = – 4
∴ S16 = `16/2[2a + (16 - 1)d]` ...`[∵ S_n = n/2[2a + (n - 1)d]]`
= 8[2 × 10 + 15(– 4)]
= 8(20 – 60)
= 8(– 40)
= – 320
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