Question

You have been asked to set up chairs for the school concert. The first row will have 10 seats, and each additional row has 4 seats more than the previous row. How many seats are there in row 20?

Answer 1

Hello!

This is a question about an arithmetic sequence. We can solve it using the formula:

`a_n=a_1+(n-1)\cdot r`

Let's replace them with the values mentioned in the exercise:

`\begin{gathered} a_(20)=10+(20-1)\cdot4 \\ a_(20)=10+19\cdot4 \\ a_(20)=10+76 \\ a_(20)=86 \end{gathered}`

Answer:

86 seats in row 20.