Question

if second and third terms of an A.P are 24and 28 respectively ,then find the sum of first 61 terms
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Answer 1

$a2 = 24$

$a3 = 28$

Difference

$d = 4$

$a1 = a2 - 4$

or

$a1 = 20$

A.P = 20, 24, 28, ...

For finding the nth term

$an = a + (n - 1) \: d$

$a61 = 20 + (61 - 1) \times 4$

$a61 = 260$

a61 = 260