Answer:
-13°C
Step-by-step explanation:
The number of hours from midnight to 9:00 am is 9 hours.
If the temperature dropped 1.25°C each hour then:
[tex]\begin{aligned}\implies \textsf{Total degrees temperature dropped}& = \sf Number\; of \;hours \times rate\\&=\sf 9\;h \times 1.25^{\circ}C/h\\&=\sf 11.25^{\circ}C\end{aligned}[/tex]
If the temperature at 9:00 am was -24.25°C then:
[tex]\begin{aligned}\implies \textsf{Temperature at midnight}& = \textsf{Temperature at 9:00 am}+\textsf{Total degrees dropped}\\&=\sf -24.25^{\circ}C+11.25^{\circ}C\\&=\sf -13^{\circ}C\end{aligned}[/tex]
Therefore, the temperature at midnight was -13°C.