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Let `a_(1),a_(2),a_(3), . . .,a_(100)` be an arithmetic progression with `a_(1)=3andS_(p)=sum_(i=1)^(p)a_(i),aleple100`. For any integer n with `1lenle20`, let m=5n. If `(S_(m))/(S_(n))` does not depend on n, then `a_(2)` isA. 9B. 8C. 7D. 5 |
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Answer» Correct Answer - A Since `a_(1),a_(2),a_(3), . . . .,a_(100)` is an A.P. with `a_(1)=3andS_(p)=underset(i=1)overset(p)suma_(i)`. `:." "(S_(m))/(S_(n))=(S_(5n))/(S_(n))=((5n)/(2){2xx3+(5n-1)xxd})/((n)/(2){2xx3+(n-1)xxd})=(5(5nd+6-d))/((nd+6-d))` Clearly, it will be independent of n if 6-d=0 i.e. d=6. `:." "a_(2)=a_(1)+d=3+6=9` |
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