Find the term of the arithmetic progression 9,12,15,18,............. which is 39 more than its 36th term.
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Find the term of the arithmetic progression 9,12,15,18,............. which is 39 more than its 36th term.
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ans
Given: 9,12,15,18,.. are in A.P
where a=9 and d=12−9=3
t
n=39+t
36
(given)
t
36
=a+35d=9+25×3=9+105=114
t
n
=39+t
36
=39+114=153
⇒a+(n−1)d=153
⇒9+(n−1)×3=153
⇒(n−1)×3=153−9=144
⇒(n−1)=
3
144
=48
⇒n=48+1=49
∴ the 49
th
term is 153 from above