if an=45,a=3,Sn=300,find d and n

Asked by  | 31st Jan, 2009, 11:43: AM

Expert Answer:

an = a + (n-1) d

Sn = (n/2)(2a + (n-1) d)

We have, an = 45, a =3, Sn =300

On substitution

45 = 3 + (n-1) d

42 = (n-1) d.................(1)

300 = (n/2) (6+ (n-1)d)

600 = n (6+42)

n = 600/48....................(2)

Now from (1) and (2)

Calculate d & n

 

Answered by  | 31st Jan, 2009, 01:02: PM

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