# The sum of n terms of two ap are in ratio (5n+4) : (9n+6) Find the ratio of their 18th term?plzz reply with solution

Let a1a2, and d1dbe the first terms and the common difference of the first and second arithmetic progression respectively.

According to the given condition, Substituting n = 35 in (1), we obtain  From (2) and (3), we obtain Thus, the ratio of 18th term of both the A.P.s is 179: 321.

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y do you substitute n=35 in (1) .............. pls help...........

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because (18+18)-1 =35

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idk exactly

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ugh

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Hey . We are taking n=35 becoz we need to find the 18th term.. As the eqn comes 2a1+34d1 2a2+34d2 respectively .. Take 2 common and u will get a1+17d1 a2+17d2 resp. So u get the desired answer. I hope its clear to u .. 😊
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thnx
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How did u get n=35n why
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Why n=35?
We need to find 18th term of both the ap's. Now a18= a + (18-1)d = a + 17d
If we substitute n=35 and take 2 as common we will get   a+17d form in both the terms.
Therefore in order to get this we randomly substitue 35 in n.
Hope this helped  @Harman Brar
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Why n=35?
We need to find 18th term of both the ap's. Now a18= a + (18-1)d = a + 17d
If we substitute n=35 and take 2 as common we will get   a+17d form in both the terms.
Therefore in order to get this we randomly substitue 35 in n.

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how is n 35

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how is n=35?
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why cant we do directly when we get a+(18-1)d=a+17d

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poora answer post kro yar..kuch smajh hi nhi arha pta nhi kya likhe ho
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But why n=35???
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Hey! this is the answer to why n=35? Suppose we want to get a19 th terms ? then a19=a+(19-1)=a+18d now notice 18 .(n-1) multiply it with 2 . we get 36. now ques. urself how to get T36th . ans. You need to subtract 1 from 37 (substituting this value=37 in eqn.), then only u'll get a+18d form .,(since we take 2 common and what remains inside is a1+18d) thanks! Hope it helps. any mistake pl reply me .!
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how did u get n=35?

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to get an=  a+17d we subsitute n= 35

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But in such kinds of such kinds of sums, how are we going to know about the value to substitute in place of 'n'? In the above answer, how we took 'n'= 35?
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We are taking n=,35 because it is a rule ro substitute the value of n =2(the desired term ) -1
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In RD Sarma book, the question is different - ratio is given as 5n+9/9n+6, but the answer given as the same (179/321).
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yes yes hello hello bye bye for or
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There is a formula to find the ratio of mth terms when the ratio of nth term is given the formula is 2m-1 Hence to find the ratio of 18th term 35 is substituted
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Why we take n = 35 ? Explain
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We took n=35......because we took the formula (2n-1)....?
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If we want to find 25 term so what value we should substitute for n?
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Tq friends
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look, 2a+(n-1)d can be written as
a+ [(n-1)/2]d
This is of the general form of any term in an A.P. i.e. a+(n-1)d
As we have to find ratio of 18th term,
We need to equate (n-1)/2  and n-1
So, n-1/2 = 17
n-1=34
n=35
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Hope this helps!!! • 4
Why n=35?
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Hope this helps you • 5
Reason why n=35 • 4
the sum of n terms of AP's is in the ration ( 5n  +4 ) : ( 9n +6). Find the ratio of their 18th term
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N=35 kese aya
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