Question

Sandra plans to fill a corner of her yard with decorative stones. Each row has six more stones than the prior row.

Part 1: If there were five stones in the first row, how many stones were used to fill all 40 rows?

Part 2: Using complete sentences, explain the procedure taken to answer this question.

Answer 1

i think in this one you use arithmetic sequence or series

Answer 2

an = a1 + (n-1)d
or
Sn = n/2 (a1+an) or Sn = n/2[2a1 + (n-1)d]

Answer 3

use the arithmetic series one :D

Answer 4

Okk can you help me ?

Answer 5

1 5
2 5+6
3 5+6*2
...
so it looks like 5+6*(r-1)
40 5+6*(40-1) =239
Lets look at the formulas
http://www.purplemath.com/modules/series4.htm

The formula for the first n terms of an arithmetic sequence, starting with n = 1, is:
(n/2)*(a1+an)
(40/2)*(5+239)=4880

i'd dbl check tho

Answer 6

on second thought i am pretty sure i am right :D

Answer 7

Yes you are (: thanks you so muchh ((:

Answer 8

ooh another example
1 5 =5
2 5+6 =11
3 5+6*2 =17
...
so it looks like 5+6*(r-1)
40 5+6*(40-1) =239

so the sequence is 5,11,17 ... 40
The series is 5+11+17...+40