p132 #42

[rfulky]

The way i solved this problem is as follows. It is wrong but can someone please explain to me my error in logic.

Know:
e/3 = cost of one leg of round trip flight
e = cost of the first leg of the initial flight

Question:
How much is the total cost of n round-trip tickets for one customer.

My solution (wrong):

first leg (e) + second leg (e/3) = first round trip ticket = 4e/3

2 * (e/3) * n = every subsequent round trip ticket ticket = 2n(e/3)

first round trip ticket + every other subsequent round trip ticket = total cost

4e/3 +2n(e/3) = (4e + 2ne)/3

Were did I go wrong?
Thanks for the help!

[TY]

Your mistake is here:
2 * (e/3) * n = every subsequent round trip ticket ticket = 2n(e/3)
It should be n-1, since the first round-trip was calculated separately.

This problem has been revised in our latest version of our book dated Jan 27, 2008. However, the problem remains essentially the same as the previous one other than different wording.

Here it is:

42. A budget airline charges each customer e/3 euros for every leg of the flights between London and Ibiza. The only exception is that it charges e euros for the first leg of the first round-trip for the same customer. How much is the total cost of n round-trip tickets for one customer?

The answer is B.

Solutions:
e (first leg);
e/3 (second leg);
then each leg is e/3 for 2(n-1) legs

Total cost is: e+e/3+(e/3)*2(n-1) = (2e+2en)/3

Tracy