Problem: Article: This can help you check that your answer is reasonable. To estimate, round whatever numbers you are working with to numbers that you can easily manipulate in your head. Then perform the calculation and note the estimated value. When you complete the calculations using the actual numbers, compare how close your answer is to your estimate. If it is in the ballpark of your estimate, you know your calculations are likely correct. For example, if you are calculating 11,87639{\displaystyle 11,876\div 39}, you can round 11,876 up to 12,000, and 39 up to 40. Then, you can calculate in your head using basic math facts that 12,00040=300{\displaystyle 12,000\div 40=300}. Then complete you exact calculation. If you get that 11,87639=304{\displaystyle 11,876\div 39=304}, remainder 20{\displaystyle 20}, you can see that your answer and estimate are close, and therefore your calculation is likely correct. You shouldn't use a calculator to complete your math work, unless your teacher tells you it is okay. However, there is nothing wrong with using a calculator to check your answer once you have finished calculating. If you discover with the calculator that your answer is incorrect, don't simply change your answer. Go back through your work and see where you made a mistake in the calculating process, then show the necessary work needed to find the right answer. If you don't show your work on a math problem, your teacher might think you did everything on a calculator and won't give you any credit. Inverse operations are opposite operations that undo one another. Addition and subtraction are inverse operations. Multiplication and division are inverse operations. You can create true equations with the same three numbers using inverse operations. For example, if you find that 56016=35{\displaystyle 560\div 16=35}, you should be able to make a multiplication problem with the same three numbers by multiplying the divisor (the number you are dividing by) by the product: 1635=560{\displaystyle 16 imes 35=560}. If the equation you make with the inverse operation is true, then your calculation is correct.
Summary: Make an estimate. Use a calculator. Use the inverse operation.

Problem: Article: While oven cleaner can be effective in getting rid of scorch marks, it should be used as a last resort because it is extremely caustic and may discolor the pan. You should never use it on a pan with a non-stick or other protective coating, though, because it will strip off the coating and ruin the pan. Because oven cleaner has the potential to damage cookware, you should only use it if you've tried other methods of cleaning your scorched pan and they've failed. If you're planning to toss the pan anyway, it's a worth a try to use the oven cleaner. Oven cleaner contains caustic chemicals that give off very strong fumes, so it's important to take safety precautions before you use it. Cover your hands with a pair of rubber gloves to keep your skin safe from the chemicals. You should also make sure that your kitchen is well-ventilated before spraying the oven cleaner, so open a window or two if possible. If you're especially sensitive to fumes, you may want to wear a dust mask over your nose and mouth when you're using the oven cleaner. Be sure to read all of the safety warnings on the oven cleaner's packaging so you're aware of any other safety precautions that you should take. Once you're prepared to work with the oven cleaner, spray it over the scorched areas of the pan. Because the cleaner is so caustic, you don't want to use any more than is necessary so cover the bottom of the pan with a light layer. You can use a brush to ensure that it's spread over the entire pan. While spray oven cleaners formulas are usually the most common, you can also find cream and foam formulas that may work better when you're cleaning a scorched pan. In order for the oven cleaner to fully penetrate the scorched areas and loosen the film and debris, you need to let it sit on the pan for at least a half hour. Because of the fumes, it's best to place the pan outside while the cleaner on it. Cover the pan with a lid, and set it on a table or ledge outside your home. If you don't have any area outside that you can set the pan, open a window and set it on the window ledge. After the cleaner has sat on the pan for approximately a half hour, use a scrub brush or sponge to scour the pan. The scorched film and debris should lift right off. Once you've cleaned the pan completely, make sure to rinse it extremely well to ensure that there's no residue from the oven cleaner left on the surface. If you're concerned about oven cleaner residue being left behind on the pan, wipe it down with a dry towel after you've rinsed it initially to see if anything comes off on the towel. You should definitely rinse it again if you notice any film, though you may want to rinse it again even if the pan is clean to be safe.
Summary:
Make sure your pan isn't non-stick. Put on gloves and open a window. Apply oven cleaner to bottom of the pan. Cover and set outside. Scrub the pan clean and rinse well.