Ryan bought some files at $3 each. He later sold them to his customers at $5 each. For customers who bought two files were given another file for free. The customers bought either one or two files. Ryan gave away 110 free files and collected a total of $1050 more than what he had paid for. How many customers bought just one file each?

	Files sold	Files given to customers who got 1 file each	Files given to customers who got 3 files each
Number	1 u	1 u - 330	330
Value	$3	$5	$5
Total Value	3 u	5 u - $1650	$1100

Since 110 files were given free, there were 110 customers who bought two files each.

Number of files that each customer would get if they bought two files each and got 1 file free
= 2 + 1
= 3

Total number of files for customers who each bought two files 
= 3 x 110
= 330

Number of files for customers who each bought 1 file = 1 u - 330

Total amount collected from customers who bought 1 file each
= 5 x (1 u - 330)
= 5 u - 1650

Total amount collected from customers who bought two files each
= 110 x 2 x 5
= $1100

Total amount collected from all the customers
= 5 u - 1650 + 1100
= 5 u - 550

Ryan collected a total of $1050 more than what he had paid for.

5 u - 550 = 3 u + 1050
5 u - 3 u = 1050 + 550
2 u = 1600

1 u = 1600 ÷ 2 = 800

Number of customers who bought just one file
= 1 u - 330
= 800 - 330
= 470

Answer(s): 470