which term of A.P:3, 15, 27, 39,............. will be 120 more than its 21st term
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Step-by-step explanation:
A. P 3,15,27
A21=3+20*12
=243
3+(n-1)12=243+120
(n-1)12=363-3
n-1=360/12
n-1=30
n=31
21st term= a+20d=3+240=243
120more=243+120=363
363 is some nth term
It can be written as 3+(n-1)d
363=3+(n-1)12
n=31
Therefore and is 31st term