The bird park tickets are priced at $28 and $19.  The number of $28-dollar tickets available is  1¹₃ that of the number of $19-dollar tickets. 3 out of 5 of the $28-dollar tickets and all the $19-dollar tickets were sold. The ticket sales amounted to $3105. How much more would have been collected if all the tickets were sold?

	$28	$19
Comparing $28 and $19 tickets at first	4x5 = 20 u	3x5 = 15 u
Before	5x4 = 20 u
Change	- 3x4 = - 12 u	- 15 u
After	2x4 = 8 u	0 u

The number of 28 tickets at first is repeated.  Make the number of 28 tickets the same.  LCM of 5 and 4 is 20.

1¹₃ = ⁴₃

Number of $28 tickets : $19 tickets = 4 : 3

	$28	$19	Total
Number	12 u	15 u
Value	$28	$19
Total value	336 u	285 u	$3105

Total amount collected from the sale of the sold tickets
= 336 u + 285 u
= 621 u

1 u = 3105 ÷ 621 = 5

Number of $28-tickets left unsold
= 8 u 
= 8 x 5
= 40

More amount to be collected if all the tickets were sold
= 40 x 28
= $1120

Answer(s): $1120