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Asked by  | 22nd Jun, 2009, 11:09: PM

Expert Answer:

Let the middle term be a.So it's given that a=20

Since out of 11 terms, the middle term has to be the 6th term, so it means that the 6th term is a=20.

Let the comon difference be d.

So the 5 terms before the 6th tem are

a-5d ,a-4d,a-3d,a-2d,a-d

the 5terms after the 6th term will be

a+d, a+2d, a+3d, a+4d, a+5d

Since the sum of the 11 terms is

=(a-5d)+(a-4d)+....(a-d)+(a)+(a+d)...+(a+5d)

=11a

So the required sum is 11a=220.

Answered by  | 23rd Jun, 2009, 01:11: AM

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