Question

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?

Answer 1

we know that

In an Arithmetic Sequence the difference between one term and the next is a constant

This problem is an Arithmetic Sequence

where

the first term is $23$

and

the common difference is $-2$

In general we can write an Arithmetic Sequence as a rule

$an=a1+d*(n-1)$

where

a1 is the first term

d is the common difference

so

$a1=23\\\\ d=-2$

Find the term a7

$an=a1+d*(n-1)\\ \\ a7=23+(-2)*[7-1]\\ \\\\ a7=23-12\\ \\\\ a7=11$

therefore

the answer is

$11\ tiles$

Answer 2

There will be 11 tiles in the 7th row, Hope this helped! :)