If the 9th term of an A.P. is 16, then find the sum of the first 17 terms of this A.P.
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Answer:
272
Step-by-step explanation:
ATQ
A9 = 16
A + 8D = 16 ----------- 1st equation
S17 = 17/2 [2a + (n-1)d]
S17 = 17/2 [ 2a + ( 17 - 1) d]
S17 = 17/2 [ 2a +16d]
= 17/2 [ 2(a +8d)]
= 17/2 [ 2 × 16 ] ---------- from 1st equation
= 17/2 ( 32 )
= 272
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