Posted by azmeerahim on Saturday, February 9, 2013 at 12:28pm.
The sixth term of an arithmetic progression is 265 and the sum of the first 5 terms is 1445. Find the minimum value of n so that the sum of the first n terms is negative.

Math  Steve, Saturday, February 9, 2013 at 2:28pm
a+5d = 265
5/2 (2a+4d) = 1445
(a,d) = (305,8)
So, we want
n/2 (2a+(n1)d) < 0
n/2 (2*305 + (n1)(8)) < 0
n > 77.25
so, you need 78 terms before the sum is negative
makes sense, since the 39th term is negative, so you need another 39 terms to offset the first 39.
Answer This Question
Related Questions
 maths  1) The first term of arithmetic progression is 20 and the sum of it's ...
 Maths  1..The first 2 terms of a geometric progression are the same as the ...
 math  An arithmetic progression as the same first and second terms as the ...
 algebra 2  An arithmetic progression has 5 terms that have a sum of 200. The ...
 kite  the sixth term of an arithmetic progression is 21 and the sum of the ...
 math  An arithmetic series is such that the 10th term is 40 and the sum of the ...
 math C2 sequences and series  The eight,fourth and second terms of an ...
 Math  An arithmetic progression has 10 terms. Sum of the 10 terms is 220. Sum ...
 maths  the sum of the 4th and 6th terms of an A.P is 42. the sum of the 3rd and...
 Mathematics  The 25 term of an Arithmetic Progression is 7 1/2 and the sum of ...
More Related Questions