Fabian bought some markers at $6 each. He later sold them to his customers at $11 each. For customers who bought two markers were given another marker for free. The customers bought either one or two markers. Fabian gave away 100 free markers and collected a total of $1400 more than what he had paid for. How many customers bought just one marker each?

	Markers sold	Markers given to customers who got 1 marker each	Markers given to customers who got 3 markers each
Number	1 u	1 u - 300	300
Value	$6	$11	$11
Total Value	6 u	11 u - $3300	$2200

Since 100 markers were given free, there were 100 customers who bought two markers each.

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

Total number of markers for customers who each bought two markers 
= 3 x 100
= 300

Number of markers for customers who each bought 1 marker = 1 u - 300

Total amount collected from customers who bought 1 marker each
= 11 x (1 u - 300)
= 11 u - 3300

Total amount collected from customers who bought two markers each
= 100 x 2 x 11
= $2200

Total amount collected from all the customers
= 11 u - 3300 + 2200
= 11 u - 1100

Fabian collected a total of $1400 more than what he had paid for.

11 u - 1100 = 6 u + 1400
11 u - 6 u = 1400 + 1100
5 u = 2500

1 u = 2500 ÷ 5 = 500

Number of customers who bought just one marker
= 1 u - 300
= 500 - 300
= 200

Answer(s): 200