A) 715
B) 702
C) 615
D) 602
E) 589
Correct Answer: B
Solution :
The required natural numbers are \[12,19,26,33,40,47,54,61,68,75,82,89,96\] \[\therefore \] \[Sum=12+19+26+33+40+47+54\] \[+61+68+75+82+89+96\] \[=702\] Alternate The required natural numbers are \[12,\text{ }19,\text{ }26,\text{ }...,96\] Let there are n terms in this series. Then last term \[=96=12+(n-1)7\] \[\Rightarrow \] \[n-1=\frac{84}{7}=12\] \[\Rightarrow \] \[n=13\] Now, sum of these terms \[{{S}_{13}}=\frac{13}{2}[24+12\times 7]=\frac{13}{2}\times 108\] \[=13\times 54=702\]You need to login to perform this action.
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