Question
The sum of the first 10 terms of an arithmetic sequence
is 60 and the 10th term is 5. What is the first term of the sequence?Solution
Sn = (n/2) [2a + (n - 1)d] 60 = 10/2 [2a + (10 - 1)d] 60 = 5 [2a + 9d] 2a + 9d = 12 ------ (i) Given 10th term is 5, so => a10 = a + 9d => a + 9d = 5 ------ (ii) Solving eqn (i) and (ii) we get, => a = 7
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