Find the sum of the series 57, 55, 53, …………….. 17.
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Answered by
0
Answer:
174.25
Step-by-step explanation:
a=57
d=-2
n=17
Sn=n/2 [2a+(n-1)d]
=17/2 (114-32)
=17/2×82
=174.25
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Answered by
1
Step-by-step explanation:
A1=57 ,A2 = 55, A3 = 53
d = A2-A1
D = 55 -57
d =-2
n=?
An = 17
An = A + (n-1) d
17 = 57 +(n-1) -2
17 -57=(n-1)-2
-40÷-2= (n-1)
20+1=n
21=n
Sn= n÷2(a+l)
Sn=21÷2 (57+ 17)
Sn=21÷2(60)
Sn=21×30
Sn=630
sum of the serios is 630 .
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