The zoo tickets are priced at $16 and $9.  The number of $16-dollar tickets available is  1⁵₆ that of the number of $9-dollar tickets. 3 out of 5 of the $16-dollar tickets and all the $9-dollar tickets were sold. The ticket sales amounted to $3990. How much more would have been collected if all the tickets were sold?

	$16	$9
Comparing $16 and $9 tickets at first	11x5 = 55 u	6x5 = 30 u
Before	5x11 = 55 u
Change	- 3x11 = - 33 u	- 30 u
After	2x11 = 22 u	0 u

The number of 16 tickets at first is repeated.  Make the number of 16 tickets the same.  LCM of 5 and 11 is 55.

1⁵₆ = ¹¹₆

Number of $16 tickets : $9 tickets = 11 : 6

	$16	$9	Total
Number	33 u	30 u
Value	$16	$9
Total value	528 u	270 u	$3990

Total amount collected from the sale of the sold tickets
= 528 u + 270 u
= 798 u

1 u = 3990 ÷ 798 = 5

Number of $16-tickets left unsold
= 22 u 
= 22 x 5
= 110

More amount to be collected if all the tickets were sold
= 110 x 16
= $1760

Answer(s): $1760