Level: Year 4, Year 5 and Year 6
Author: Cassandra Lowry
Estimation is a skill that many of use on a regular basis, think of cooking or driving a car, but we often do not say “I estimate…”. At school, estimation is part of the curriculum from the beginning. Early on children are encouraged to estimate the number of objects in a collection, then later check the total. By the end of Year 5, children are encouraged to use estimation to help them make reasonable guesses at solutions and to check the accuracy of their calculations.
Basically, estimation is about finding an answer to a problem (often quickly) that is “close enough” to the right answer to help us. For example, if we only had $20 to buy food and we knew that the four items we wanted to buy were each less than $5 we could quickly estimate (as 4 x 5 = 20) that we would have enough money.
Estimation can also help children to check whether their calculations are valid. For example, if we wanted to find 19 x 5, we might think that 20 x 5 is 100, so 19 x 5 must be less than that. Here we have “rounded” 19 to the nearest ten. This process of rounding numbers can assist with making quick calculations and estimates.
Rounding is where we change numbers slightly to make calculations easier to complete mentally. For example, if I wanted to estimate a solution to the problem 33 + 66, I might round both these numbers to the nearest 10, then in my head calculate that 30 + 70 is 100. If my solution to 33 + 66 is too far away from my estimate, then I will know I may have made a calculation error.
More information on estimation and rounding can be found in the document below.
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