Exercise 1: Why APR, Not the "0%" Headline, Is the Real Comparison — Possible Solution
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A "0% for 12 months" headline only describes the interest rate portion
of the cost - it says nothing about other real costs like an
arrangement fee, which the chapter's own definition of APR is
specifically designed to fold in. Two cards can share the exact same
0% headline rate while genuinely costing different real amounts,
purely because of a fee one of them charges and the other doesn't.

The card with the £50 arrangement fee is genuinely more expensive
overall than the fee-free card, even though both show an identical
0% interest figure - the £50 is a real cost that has to be paid
regardless of the 0% rate, while the other card has no equivalent
cost at all. Comparing only the headline "0%" figure would make the
two cards look identical when they genuinely aren't; comparing their
real APR figures (which account for the fee) would correctly reveal
the fee-charging card as the more expensive option.

ANSWER: Comparing APR rather than the "0%" headline is correct because
APR folds in real additional costs like the £50 arrangement fee, which
the interest rate alone doesn't capture. Even though both cards show
identical 0% interest, the card with the fee is genuinely more
expensive - a difference the headline rate alone hides but the real
APR figure reveals.

WHY THIS WORKS AS AN ANSWER
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This correctly applies the chapter's own APR-vs-interest-rate
distinction to a concrete scenario where the two products look
identical on the surface but genuinely aren't, rather than treating
the "0%" headline as the complete picture.