How long will it take a dish to bake at 275 degrees that should be baked 350 for 1hr 30 minutes?

You can't simply calculate the baking time by directly scaling the temperature down. Here's why:

* Heat Penetration: Lowering the temperature slows down the heat transfer into the food.

* Moisture Loss: Baking at a lower temperature for a longer time can lead to more moisture loss, which can affect the texture of your dish.

* Recipe Specifics: The original recipe was designed for a specific temperature and time to achieve the desired outcome.

What to do instead:

1. Check the recipe: Some recipes may include instructions for lower temperature variations.

2. Adjust based on the dish: For dishes that rely heavily on browning (like roast vegetables), a lower temperature may not be ideal. For dishes that need more gentle cooking (like casseroles), a lower temperature might be acceptable.

3. Start with a shorter time: Begin by reducing the baking time by 15-20 minutes. Check for doneness, and add more time in 5-10 minute increments as needed.

Important Note: Always use a reliable food thermometer to check for doneness, especially when adjusting baking times and temperatures.