1.

7+9+11+12+15+15........ Upto 70 terms find the sum of the series

Answer» A=7 , d=2
a = 7 =d=2 ...n =70= Sn= n/2(2a +( n-1)d) = S70 = 70÷2(2×7 + ( 70-1)2) = 35(14+138 ) = 35× 152 =2320
5320


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