Sum of first 10 terms of an arithmetic Sequence is 220 and that of first 16 terms is 244. What is the sum of first 8 terms?
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Step-by-step explanation:
S10= 10/2(a+9d)
220=5(a+9d)
220/5=a+9d
44=a+9d.....(1)
S16= 16/2(a+15d)
244=8(a+15d)
244/8=a+15d
61/2=a+15d
61=2(a+15d)
61=2a+30d....(2)
From ...(1)
a=44-9d....(3)
Putting value of a in equation(2)
2(44-9d) + 30d = 61
88-18d +30d=61
88+12d=61
12d=61-88
d=-27/12
d=-9/4
Putting value of d in equation (3)
a=44-9d
a=44-9(-9/4)
a=95/4
Hence put these a and d value in S8 formula nd you will get your ans
I hope its helpful
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