2. The sum of the first four terms of an AP is 28 and sum of the first eight terms of the same AP is
88. Sum of first 16 terms of the AP is
(2) 346
(6) 340
(C) 304
(d) 268
Answers
Answered by
40
S4=28
S8=88
S16=?
S4=n/2[2a+(n-1)d]
28=4/2[2a+3d]
14=2a+3d equation. 1
S8=8/2[2a+7d]
88=4[2a+7d]
22=2a+7d equation. 2
Subtract both
14=2a+3d
22=2a+7d
- - -
-8=-4d
D=2
22=2a +14
a =4
n/2[2a+15d]
8[8+30]
8×38
304
Answered by
20
Answer:
The answer of this question is option C
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