Oliver bought some staplers at $3 each. He later sold them to his customers at $7 each. For customers who bought two staplers were given another stapler for free. The customers bought either one or two staplers. Oliver gave away 120 free staplers and collected a total of $2360 more than what he had paid for. How many customers bought just one stapler each?

	Staplers sold	Staplers given to customers who got 1 stapler each	Staplers given to customers who got 3 staplers each
Number	1 u	1 u - 360	360
Value	$3	$7	$7
Total Value	3 u	7 u - $2520	$1680

Since 120 staplers were given free, there were 120 customers who bought two staplers each.

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

Total number of staplers for customers who each bought two staplers 
= 3 x 120
= 360

Number of staplers for customers who each bought 1 stapler = 1 u - 360

Total amount collected from customers who bought 1 stapler each
= 7 x (1 u - 360)
= 7 u - 2520

Total amount collected from customers who bought two staplers each
= 120 x 2 x 7
= $1680

Total amount collected from all the customers
= 7 u - 2520 + 1680
= 7 u - 840

Oliver collected a total of $2360 more than what he had paid for.

7 u - 840 = 3 u + 2360
7 u - 3 u = 2360 + 840
4 u = 3200

1 u = 3200 ÷ 4 = 800

Number of customers who bought just one stapler
= 1 u - 360
= 800 - 360
= 440

Answer(s): 440