The zoo tickets are priced at $17 and $13.  The number of $17-dollar tickets available is  1⁴₅ that of the number of $13-dollar tickets. 3 out of 5 of the $17-dollar tickets and all the $13-dollar tickets were sold. The ticket sales amounted to $3920. How much more would have been collected if all the tickets were sold?

	$17	$13
Comparing $17 and $13 tickets at first	9x5 = 45 u	5x5 = 25 u
Before	5x9 = 45 u
Change	- 3x9 = - 27 u	- 25 u
After	2x9 = 18 u	0 u

The number of 17 tickets at first is repeated.  Make the number of 17 tickets the same.  LCM of 5 and 9 is 45.

1⁴₅ = ⁹₅

Number of $17 tickets : $13 tickets = 9 : 5

	$17	$13	Total
Number	27 u	25 u
Value	$17	$13
Total value	459 u	325 u	$3920

Total amount collected from the sale of the sold tickets
= 459 u + 325 u
= 784 u

1 u = 3920 ÷ 784 = 5

Number of $17-tickets left unsold
= 18 u 
= 18 x 5
= 90

More amount to be collected if all the tickets were sold
= 90 x 17
= $1530

Answer(s): $1530