The tourist attraction tickets are priced at $21 and $12.  The number of $21-dollar tickets available is  1¹₃ that of the number of $12-dollar tickets. 2 out of 5 of the $21-dollar tickets and all the $12-dollar tickets were sold. The ticket sales amounted to $3828. How much more would have been collected if all the tickets were sold?

	$21	$12
Comparing $21 and $12 tickets at first	4x5 = 20 u	3x5 = 15 u
Before	5x4 = 20 u
Change	- 2x4 = - 8 u	- 15 u
After	3x4 = 12 u	0 u

The number of 21 tickets at first is repeated.  Make the number of 21 tickets the same.  LCM of 5 and 4 is 20.

1¹₃ = ⁴₃

Number of $21 tickets : $12 tickets = 4 : 3

	$21	$12	Total
Number	8 u	15 u
Value	$21	$12
Total value	168 u	180 u	$3828

Total amount collected from the sale of the sold tickets
= 168 u + 180 u
= 348 u

1 u = 3828 ÷ 348 = 11

Number of $21-tickets left unsold
= 12 u 
= 12 x 11
= 132

More amount to be collected if all the tickets were sold
= 132 x 21
= $2772

Answer(s): $2772