A 1-week pass to all theme parks for one person costs $210. The management gives a concession to a group of 30 tourists. For every 3 tourists who purchase the 1-week pass, the 4th tourist gets free access to the theme parks. How much does each tourist pay in this arrangement if they share the total cost equally?
For every 3 tourists, 4th tourist gets free access.

Number of tourists in eact set
= 3 + 1
= 4

Number of sets of 4 tourists
= 30 ÷ 4
= 7 r 2 

There are 7 sets of 4 tourists in 30 tourists, so 7 tourists will get free access.

Number of tickets to be paid for
= 30 - 7
= 23

Total cost of tickets
= 23 x 210
= $4830

Cost for each tourist
= 4830 ÷ 30
= $161
 
Answer(s): $161