Write an article based on this "Make an estimate. Use a calculator. Use the inverse operation."
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 11,876÷39{\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 12,000÷40=300{\displaystyle 12,000\div 40=300}. Then complete you exact calculation. If you get that 11,876÷39=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 560÷16=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: 16×35=560{\displaystyle 16\times 35=560}. If the equation you make with the inverse operation is true, then your calculation is correct.