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

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

Answer 2

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`