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October 21, 2014

October 21, 2014

Posted by **swathi** on Friday, March 2, 2012 at 6:31am.

- arithmetic -
**drwls**, Friday, March 2, 2012 at 9:14amLet the common difference be d.

The sum of the first four terms is

5 + (5+d) + (5+d+d) + (5+d+d+d)

= 20 + 6d

The sum of the next 4 terms is

5+4d + 5+5d + 5+6d + 5+7d = 20 + 22d

You have been told that

20 +6d = (1/2)(20 + 22d)= 10 + 11d

Therefore

5d = 10

d = 2

Check: does

5+7+9+11 = (1/2)(13+15+17+19) ?

32 = (1/2)(64)

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