Friday

January 30, 2015

January 30, 2015

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)

**Answer this Question**

**Related Questions**

arithmetic - 1. The first and last term of an A.P are, a and l respectively, ...

arithmetic - 1. The first and last term of an A.P are, a and l respectively, ...

Math - 1) If the sum of the first n terms of a series is Sn where Sn=2nē-n, (a)...

math - 1) If the sum of the first n terms of a series is Sn where Sn=2nē-n, (a)...

arithmetic - the sum of the n termsof an ap whose first term is 5 and common ...

Math(arithmetic & Geometric Series) - 1)The sum of 6 terms of an arithmetic ...

maths - 1) The first term of arithmetic progression is -20 and the sum of it's ...

math - The sum of the first 20 terms of an arithmetic series is identical to the...

Precalculus - The 8th term in an arithmetic sequence is 5, and the sum of the ...

Mathematics - The 25 term of an Arithmetic Progression is 7 1/2 and the sum of ...