If the sum of n terms of two series of A.P are in the ratio
5n+4:9n+6 .find the ratio of their 13th terms

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If the sum of n terms of two series of A.P are in the ratio 5n+4:9n+6 .find the ratio of their 13t..

Answer / krishna kumar ranjan

when ever u face this type of qun..
13*2-1=25 and put it in place of n in 5n+4/9n+6

Is This Answer Correct ?    61 Yes 30 No

If the sum of n terms of two series of A.P are in the ratio 5n+4:9n+6 .find the ratio of their 13t..

Answer / akshay b menon

(5n+4)/(9n+6)=((n/2){2x+(n-1)d})/((n/2){2x'+(n-1)d'})
             =(2x+(n-1)d)/(2x'+(n-1)d')  
             =(x+{(n-1)/2}d)/(x'+{(n-1)/2}d')
         implies,
             m=(n-1)/2
             2m-1=n
          since m=13,n=25
          substituting value of n in given ratio
            (5*25+4)/(9*25+6)=129/231

Is This Answer Correct ?    45 Yes 47 No

If the sum of n terms of two series of A.P are in the ratio 5n+4:9n+6 .find the ratio of their 13t..

Answer / narayanan

Let the 2 series have the sum S(1,n) and S(2,n).
now, S(1,n):S(2,n) = (5n+4):(9n+6)
= {5(n-1)+5+4}:{9(n-1)+9+6}
= {2*(9/2)+5(n-1)}:{2*(15/2)+9(n-1)}

= [(n/2){2*(9/2)+5(n-1)}]:[(n/2){2*(15/2)+9(n-1)}]
hence nth terms will be in the ratio
T(1,n):T(2,n)= [(9/2)+5(n-1)]:[(15/2)+9(n-1)]

=>T(1,13):T(2,13)=[(9/2)+5(13-1)]:[(15/2)+9(13-1)]
=(129/2):(231/2)
=43/77

Is This Answer Correct ?    50 Yes 67 No

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