Saturday

April 18, 2015

April 18, 2015

Posted by **emi** on Saturday, June 7, 2014 at 2:30pm.

- math -
**Steve**, Saturday, June 7, 2014 at 4:26pmIf we add up terms n through n+10, then we get

(n+10)/2 (2a + (n+9)45) - (n-1)/2 (2a+(n-2)45) = 891

11a+495n = -1089

a+45n = -99

If we are adding up the first 11 terms, then a = -144 and

T28 = -144+27*45 = 1071

T45 = -144+44*45 = 1836

But, if we add up terms T5 through T15, then n=5, and a = -324 and

T28 = 891

T45 = 1656

Better tie down your conditions a bit better

**Answer this Question**

**Related Questions**

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)...

Math - Sum of4th and the 6th terms of an a,p is 42 . While the sum of the 3rd ...

Maths - The first term of an AP is 12 and that of a GP is 6. The common ...

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

Math - The first three terms of a GP are also the first,nineth and eleventh ...

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

maths - the sum of the 4th and 6th terms of an A.P is 42. the sum of the 3rd and...

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

Math - What is the common difference of an arithmetic sequence if the sum of the...