In not so complicated math problems, a rough estimate or mentally-calculated estimate, sometimes referred to as a "ballpark estimate," helps to predict the numerical range the final answer should fall within. For example, if the given problem is to determine the sum of 23 plus 76, it can be estimated that the final and precise answer will be somewhere close to 100 because the known calculation 25 plus 75 equals 100 is close to the given problem 23 plus 76.