Final answer:
To find the dawn temperature, subtract the 9° drop from the dusk temperature of 5°C, which gives a result of -4°C at dawn.
Step-by-step explanation:
The temperature is 5°C at dusk. If at dawn it is 9°C colder than at dusk, we need to subtract 9 from the dusk temperature to find the dawn temperature.
Step-by-Step Solution:
Start with the temperature at dusk: 5°C.
Subtract the difference in temperature between dusk and dawn: 5°C - 9°C = -4°C.
The answer is the new temperature at dawn: -4°C.
Therefore, the temperature at dawn is -4°C.
According to the information provided, astronomers define morning twilight as beginning when the Sun is 18° below the horizon. Therefore, at dusk when the temperature is 5°, the Sun is still above the horizon. It is stated that it is 9° colder at dawn, which means it is 9° below the morning twilight temperature. So, if the temperature at dusk is 5°, at dawn it would be 5° - 9° = -4°.