Question 46
In a country with $n$ cities, there is a recurrent one-way flight between every pair of cities. Every flight has a constant price in the range $\$100, \$120, \$140, \$160, \$180$. A $\$N$ flight ticket gives unlimited access to flights which cost $\$N$, and tickets can be traded for tickets of lower prices. For example, with a $\$160$ ticket, Bob could take a $\$160$ flight, trade his ticket for a $\$120$ ticket, then take a $\$120$ flight.
Aerith loves flying and wonders how many successive flights she can take with one ticket. What is the minimum $n$ needed to guarantee that she can take 4 such flights in a row?
Aerith loves flying and wonders how many successive flights she can take with one ticket. What is the minimum $n$ needed to guarantee that she can take 4 such flights in a row?