A flight leaves at \(22\ 45\) and lands at \(06\ 20\) the next day. Work out the length of the flight.

This tests a duration that crosses midnight. Split the journey at midnight so that both pieces are ordinary forward-counting times.

1. From \(22\ 45\) to midnight is \(1\) hour \(15\) minutes [M1], because \(15\) minutes takes the clock to \(23\ 00\) and a further hour reaches \(24\ 00\).
2. From midnight to \(06\ 20\) is \(6\) hours \(20\) minutes [M1].
3. Add the two parts: \(1\) hour \(15\) minutes \(+\ 6\) hours \(20\) minutes \(=\ 7\) hours \(35\) minutes [A1].

Subtracting the clock readings directly, \(06\ 20 - 22\ 45\), gives a negative result and is the main pitfall. Splitting at midnight avoids it. As a check, \(22\ 45\) plus \(7\) hours is \(05\ 45\), and a further \(35\) minutes gives \(06\ 20\).