The sum of 1st and 8th terms of an arithmetic sequence is 30 . Its 4th term is 10 .
Find the 5th term of the sequence .
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Answer:
a1+a8=30
a1+a1+7d=30
2a1+7d=30 equation 1
a4=a1+3d=10 equation 2
From equation 2 a1=10-3d
Put this value of a1 in equation 1
2(10-3d)+7d=30
20+d=30
d=10
a1=10-3×10=-20
a5=-20+4×10=20 Ans
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