Question

A drive-in theater has spaces for 20 cars in the first parking row, 22 in the second, 24 in the third, and so on. If there are 21 rows in the theater, find the number of cars that can be parked. ?

Answer 1

840 cars

Explanation:

Let's write an arithmetic sequence formula to represent this:

`a_n=20+2(n-1)`

In the 21st row there are:
`a_(21)=20+2(21-1)`

`a_21=60`

Now using the sum formula for arithmetic sequences, we can find the total cars in 21 rows:

`S_(21)= 21/2(20+60)=840`