#20 - The price of a full fare coach ticket from Toronto to

[8scn]

Hello

What was the thinking process used to get B as the correct answer? I was deciding between B and C but wouldn’t figure out which was best.

[Nikki Siclunov]

The argument is structured as follows:

Premise: Full-fare Toronto-to-Dallas tickets cost the same today as they did a year ago.

Premise: A year ago, there was a 50/50 split between full-fare and discount tickets.

Premise: Today, 90% are discounted and only 10% are full-fare.

Conclusion: On average, people pay less today for a Toronto-to-Dallas ticket than they did a year ago.

Just because a greater proportion of the tickets are discounted today does not mean that people, on average, are paying less. What if the discount was 80% off full-fare tickets a year ago, whereas today it is only 20%? Then even if we have more discounted tickets, it is entirely possible that the average price is higher. In your prephrase, you should be looking for an answer addressing the cost of discount tickets today relative to their cost last year. If they cost the same (or less), the conclusion makes sense.

If (B) is assumed, the conclusion would be justified. Let's use the Justify Formula. Add (B) to the premises of the argument and see if they are sufficient to draw the conclusion:

Premise: Full-fare Toronto-to-Dallas tickets cost the same.

Justify (B): Discount Toronto-to-Dallas tickets cost the same.

Premise: The proportion of discount Toronto-to-Dallas tickets today is higher than it was a year ago.

Conclusion: Customers are paying less, on average, for a Toronto-to-Dallas ticket.

Because (B) is sufficient to justify the conclusion of the argument, it is the correct answer choice.

(C) is irrelevant. We know, from the first premise in the argument, that the full-fare coach ticket to Dallas costs the same. Even if all full-fare coach tickets on Breezeway cost the same, that wouldn't make our conclusion any better. The cost of a full-fare ticket from New York to Atlanta, or Chicago to Detroit, falls outside the scope of this argument and is entirely irrelevant to proving the conclusion.

[OriginalJane]

Hello,

I don't understand why answer D is wrong for this question. If more people are buying tickets, doesn't that arguably make it more likely that the average price of a ticket will decrease? Or, is this line of thought beyond the scope of the question, since the stimulus mentions nothing about maintaining the same level of revenue and/or profit?

Thank you,

Amanda

[Jon Denning]

Hey Jane,

Thanks for the question! This is a tricky Justify question with some Numbers and Percentages reasoning involved, so let's start by thinking about what Justify requires, and then tackle the argument itself.

Justify questions ask for an answer that, when added to the premises in the stimulus, will show that the author's conclusion is entirely valid. To that end it's wise to break the argument down into its component pieces, where hopefully we can see what might be missing. Here's question 20:

Premise 1: The price of a full fare ticket on BA (Breezeway Airlines) is the same today as it was a year ago.

Premise 2: 90% of tickets sold now are discount and 10% are full, compared to a year ago when it was 50/50 discount/full.

Conclusion: On average people pay less today overall than they did a year ago.

On the face of it, this makes sense: full fare prices are the same, but the proportion of people buying those fares (more expensive than discount, obviously) has dropped from 50% to just 10%, so that should really reduce the overall amount paid by customers. But think about what could invalidate that conclusion! What if the "discount" ticket price went way up, possibly even to nearly the same amount as a full fare? If that were the case, then even going from 50% discount sales to 90% discount sales might not actually reduce the overall expense...it could even raise the overall costs! So to prove the costs went down, we need to make sure discount tickets didn't get more expensive.

Consider a simplified example. Over two years, 100 people are buying one of two options, the cheap option A (starts at $10 and then can vary) or the more expensive option B (starts and stays at $20). In year 1 half buy A and half buy B. In year 2, 90 buy A and only 10 buy B, and we want to make year 2 cheaper overall.

Year 1, 50/50 split: That's 50 A for $500, and 50 B for $1000. Overall total is $1500. Easy enough.

Year 2, 90/10 split: Here's where it gets interesting. If A's price goes up, say to $15, then it's possible this year saw more spending (90 A at $15 = $1350 and 10 B at $20 = $200, a total of $1550). How can we guarantee this year is cheaper? Make sure A's price doesn't go up! We could keep it the same (90 A at $10 = $900 and 10 B at $20 = $200, a total of $1100), or we could drop it; either way, year 2 is guaranteed to be cheaper.

Back to the question, answer choice (B) does exactly what we want: it tells us that the discount price has stayed the same, meaning the overall costs, whatever they might be, must indeed be lower.

Answer choice (D) on the other hand is irrelevant for two reasons: (1) carrying more people per flight doesn't necessarily mean more people overall (there could be fewer flights, after all) so that's a dangerous assumption; (2) since the conclusion is about the average (per-person) cost, then volume itself doesn't matter; whatever volume is, you're still dividing it by the number of people to find the average, so whether it's, say, 10 people paying $100 total, or 100 people paying $1000 total, the average per person is unaffected ($10 each in both cases).

I hope that helps!