Sum of the finest 65 terms un an
A.P. 18 2600, find its and term.
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Sol. S55 = 3300 [Given]
Sn = n/2[2a + (n – 1)d]
∴ S55 = 55/2[2a + (55 – 1) d]
∴ 3300 = 55/2[2a + 54d]
∴ 3300 = 55/2 × 2[a + 27d]
∴ 3300 = 55 [a + 27d]
∴ 3300/55 = a + 27d
∴ a + 27d= 60 ......(i)
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