Question

If sum of n terms of an AP 48,45,42,39... is 408 then find n​

Answer 1

Answer:

here a(first term of AP)=48

diffrence =3

by using formula an=a+(n-1)d

=408=48+(n-1)3

=408-48=3n-1

=360/3=n-1

=120+1

=121

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