Question

21th term of arithmetic sequence is 40 more than it's 11th term, sum of 1st term is275. Find comman differance, 6th term and 1st term

Answer 1

$a21 = a11 + 40 \\ a + 20d = a + 10d + 40 \\ 10d = 40 \\ d = 4$

$s1 = 275 \\ therefore \: a = 275$

$a6 = a + 5d = 275 + 5(4) = 275 + 20 = 295 \\ a6 = 295$

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