Let 3,6,9,12, ldots upto 78 terms and 5,9,13,17, ldots upto 59 terms be two series. Then, sum of ter

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8. Sequences and Series

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Let $3,6,9,12, \ldots$ upto $78$ terms and $5,9,13,17, \ldots$ upto $59$ terms be two series. Then, the sum of the terms common to both the series is equal to

A

$2222$

B

$2223$

C

$2224$

D

$2225$

(JEE MAIN-2022)

Solution

For series of common terms

$a =9, d =12, n =19$

$S _{19}=\frac{19}{2}[2(9)+18(12)]=2223$

Standard 11

Mathematics

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