The safari park tickets are priced at $21 and $15.  The number of $21-dollar tickets available is  1³₅ that of the number of $15-dollar tickets. 2 out of 3 of the $21-dollar tickets and all the $15-dollar tickets were sold. The ticket sales amounted to $1683. How much more would have been collected if all the tickets were sold?

	$21	$15
Comparing $21 and $15 tickets at first	8x3 = 24 u	5x3 = 15 u
Before	3x8 = 24 u
Change	- 2x8 = - 16 u	- 15 u
After	1x8 = 8 u	0 u

The number of 21 tickets at first is repeated.  Make the number of 21 tickets the same.  LCM of 3 and 8 is 24.

1³₅ = ⁸₅

Number of $21 tickets : $15 tickets = 8 : 5

	$21	$15	Total
Number	16 u	15 u
Value	$21	$15
Total value	336 u	225 u	$1683

Total amount collected from the sale of the sold tickets
= 336 u + 225 u
= 561 u

1 u = 1683 ÷ 561 = 3

Number of $21-tickets left unsold
= 8 u 
= 8 x 3
= 24

More amount to be collected if all the tickets were sold
= 24 x 21
= $504

Answer(s): $504