Estimation is the process of finding an estimate, or approximation, which is a value that can be used for some purpose even if input data may be incomplete, uncertain, or unstable. Estimate the size of the development product. Estimate the effort in person-months or person-hours. To find a value that is close enough to the right answer, usually with some thought or calculation involved. Example: Alex estimated there were 10,000 sunflowers in the field by counting one row then multiplying by the number of rows. Estimation means to make an idea about quantities, to judge approximate size, cost, population, etc. For students, estimating is an important skill. First and foremost, we want students to be able to determine the reasonableness of their answer. Without estimation skills, students aren't able to determine if their answer is within a reasonable range.