Posted by **sdgsd** on Thursday, November 19, 2009 at 1:39pm.

An arithmetic series has third term 11. The ninth term is 5 times the second term. Find the common difference.

- math -
**drwls**, Thursday, November 19, 2009 at 2:10pm
Let the first term be called a and the common difference be called b.

a + 2b = 11

a + 8b = 5*(a + b) = 5a + 5b

The last equation can be rewritten

4a - 3b = 0

4a + 8b = 44

11b = 44

b = 4

a = 11 - 2b = 3

The series is 3,7,11,15,19,23,27,31,35...

Note that 35 (the ninth term) is 5 times 7

## Answer This Question

## Related Questions

- Math - The fifth term of an arithmetic progression is three times the second ...
- math - if 4th term of an arithmetic progression is 3 times the 1st term nd 7th ...
- Arithmetic Sequence - Given the third term of an arithmetic sequence less than ...
- Algebra - True or False 1. – 5, – 5, – 5, – 5, – 5, … is an arithmetic sequence...
- arithmetic - in an arithmetic progression the 13th term is 27 and the 7th term ...
- math - The sum of the first 10 term of an arithmetic sequence is 145 and the ...
- Math - The sum of third and ninth terms of arithmetic series is 20 and the ...
- Arithmetic progession - The third term of an A.P is 10times more than the second...
- math - the fourth term of an arithmetic progression is equal to 3 times the ...
- math - The sum of the first 10 terms of an arithmetic series is 145 and the sum ...

More Related Questions