If (1+3+5+..... upto n terms)/(2+5+8+....... upto 8 terms) = 9 , then find the value of n
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Answered by
119
Here, a=1 and d=2 and term=n
Sn=n/2(2+(n-1)2)
=n*n
Now in second, a=2,d=3,n=8
Sn=8/2(4+7*3)=4(4+21)=100
ATQ,n*n/100=9 or n*n=900 or n=30
Sn=n/2(2+(n-1)2)
=n*n
Now in second, a=2,d=3,n=8
Sn=8/2(4+7*3)=4(4+21)=100
ATQ,n*n/100=9 or n*n=900 or n=30
Answered by
2
Answer:30
Step-by-step explanation:
in 1+3+5.....nth term
a=1 , c.d=2
Sn=n/2 (2a+(n-1)d)
=n/2 {2(1)+(n-1)2}
=n/2 {2+2n-2}
=n/2 {2n}
=n^2
in 2+5+8............8th term
a=2 , c.d=3
S8=n/2 (2a+(n-1)d)
= 8/2 {2(2)+(7)3}
=4{4+21}
=4(25)
=100
now
n^2/100 = 9
n^2=900
n=
n=30
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