# Arithmetic Sequence

• Feb 4th 2010, 09:33 PM
xeronhart
Arithmetic Sequence

Find the minimum number of terms that must be taken from the sequence 3, 5, 7, 9...so that the sum is at least 440.

TQ..
• Feb 4th 2010, 09:38 PM
pickslides
Your sequence is full of odd numbers therefore one is not the answer.

Let's try 2 numbers, I can see that 219 and 221 are in your sequence and add to the desired result. We are finished.
• Feb 4th 2010, 10:56 PM
CaptainBlack
Quote:

Originally Posted by xeronhart

Find the minimum number of terms that must be taken from the sequence 3, 5, 7, 9...so that the sum is at least 440.

TQ..

Check the wording of the problem to make sure it is not asking for how many consecutive terms of the sequence starting from the first is needed so that thier sum is at least 440

CB
• Feb 4th 2010, 11:01 PM
xeronhart
find the minimum number of terms that must be taken from the sequence 3, 5, 7, 9,...so the sum is at least 440.

we are given this formula to solve the question..
s=n/2 [2a+(n-1)d]
where,
s=sum of the first n term,
n=number of term,
a=first term,

d=common difference.

the question ask to find the value of n..

• Feb 4th 2010, 11:08 PM
VonNemo19
Quote:

Originally Posted by xeronhart

Find the minimum number of terms that must be taken from the sequence 3, 5, 7, 9...so that the sum is at least 440.

TQ..

You want

$\displaystyle \sum_{i=1}^n(2i+1)\geq440$

Or

$\displaystyle 2\frac{n(n+1)}{2}+n\geq440$.

Solve the inequality.