Sequences and Series jee mains questions | Sequences and Series Previous Year Question

(6699)

A.P. : 3, 7, 11, 15, ....., 403

$d_{1} = 4$

A.P. : 2, 5, 8, 11, ....., 404

$d_{2} = 3$

L.C.M. $(d_{1}, d_{2}) = 12$

Common terms = 11, 23, 35 ... 395

$a = 11, d = 12, a_{n} = 395$

$a_{n} = a + (n - 1) d \Rightarrow 395 = 11 + (n - 1) (12)$

$\Rightarrow \frac{384}{12} = (n - 1) \Rightarrow n = 33$

$S = \frac{33}{2} (11 + 395) = \frac{33}{2} (406) = 6699$

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