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  •  Let a1, a2, a3, ......, an, ..... be in A.P.  If a3 + a7 + a</

 Let a1, a2, a3, ......, an, ..... be in A.P.  If a3 + a7 + a11 + a15 = 72, then the sum of its first 17 terms is equal to :

Option: 1

306


Option: 2

153


Option: 3

612


Option: 4

204


Answers (1)

best_answer

Given that

a1, a2, a3, ......, an, ....  are in AP

Also given that

a3 + a7 + a11 + a15 = 72

a3 + a15 = a7 + a11  = a1 + a17 = 36

Sum of first 17 term 

\\S_{17}=\frac{17}{2}\left ( a_1+a_{17} \right )\\\\\mathrm{\;\;\;\;\;}=\frac{17}{2}\times36\\\\\mathrm{\;\;\;\;\;}=306

Posted by

Gautam harsolia

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