Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

## #1 2006-03-14 10:14:12

4littlepiggiesmom
Member

Offline

### Find sum of 100 terms in a sequence?

My daughter had to miss math class for a music event and wants me to check her answers??? So here I am looking for help~

Find the sum of the first 100 terms of the aruthmetic sequence 19, 13 ,7,.....?  We came up with b

a. -58,100
b. -556
c. _27,800
d. -55,600
e. nnone of these

## #2 2006-03-14 14:03:06

George,Y
Super Member

Offline

### Re: Find sum of 100 terms in a sequence?

c, and there is a little trick-- notice c is one half of d, and think what's in the examiner's mind to do so

X'(y-Xβ)=0

## #3 2006-03-14 23:11:36

4littlepiggiesmom
Member

Offline

Thanks!

## #4 2006-03-20 00:01:29

Jenilia
Full Member

Offline

### Re: Find sum of 100 terms in a sequence?

What is a aruthmetic sequence?

Ideas are funny little things, they won't work unless you do.

## #5 2006-03-20 00:13:18

ganesh
Moderator

Offline

### Re: Find sum of 100 terms in a sequence?

An Arithmetic Progression or sequence is such that the difference between any two successive terms of the series is the same. For example,
(1) 2, 5, 8, 11, 14, 17, ...
(2) 1, 5, 9, 14, 17, 21, .....
(3) 15, 13, 11, 9, 7, 5, 3, 1, ...
(4) 0.5, 2, 3.5, 5, 6.5, 8, 9.5 etc.
You can see that the difference between any two consecutive terms is always the same for the entire series. In example (1), it is 3, in (2) it is 4, in (3), it is -2 and in (4) it is 1.5.
The first erms of the Aritmetic Series or Progression is denoted by 'a' and the common difference by 'd'.
The nth term, tn is given by tn= a+(n-1)d and
the sum of n terms is given by
Sn= n/2[2a+(n-1)d]

Character is who you are when no one is looking.