An artist is arranging tiles in rows to decorate a wall. Each new row has 2 fewer tiles than the row below it. If the first row has 23 tiles how many tiles will be in the 7th row?
my anwer was 21
21
This is an arithmetic sequence
see : http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html
term n = a + d(n-1)
a = 23
d = -2
term 7 = 23 -2 (6)
= 11
To find the number of tiles in the 7th row, we need to determine the pattern in the number of tiles as we move from one row to the next.
We are given that each new row has 2 fewer tiles than the row below it. This means that for each subsequent row, we subtract 2 tiles.
Starting with the first row having 23 tiles, we can calculate the number of tiles in the subsequent rows as follows:
1st row: 23 tiles
2nd row: 23 - 2 = 21 tiles
3rd row: 21 - 2 = 19 tiles
4th row: 19 - 2 = 17 tiles
5th row: 17 - 2 = 15 tiles
6th row: 15 - 2 = 13 tiles
7th row: 13 - 2 = 11 tiles
Therefore, the 7th row will have 11 tiles.