Estimation – 3.OA.8

[Duane]

The last sentence in 3.OA.8 says “Assess the reasonableness of answers using mental computation and estimation strategies including rounding”. Does this only apply to two-step word problems? Is there a reason for emphasizing it with two-step word problems? It’s not that they aren’t useful things to do but estimation in particular is not mentioned elsewhere such as the 3.NBT standards where you would expect students to also use it.

[Bill McCallum]

It would be artificial to restrict estimation to two-step word problems. Note also the cluster heading in 3.MD, “Solve problems involving measurement and estimation of intervals of time, liquid volumes, and masses of objects.” Estimation is important, but shouldn’t become a huge focus, with lots of time devoted to formulaic methods for handling it. The emphasis at this level is on understanding the base ten system, which is itself the basis for number sense and good estimation skills.

[Bill McCallum]

Bill, would you be able to elaborate on why estimation and rounding is mentioned in 3.OA.8 rather than 3.NBT.2 ? I appreciate that you’ve said estimation doesn’t need to be limited to 3.OA.8, and also that it shouldn’t be a big focus, but why is it there under that standard and not also/instead in 3.NBT.2, or even 3.OA.3 or 3.OA.4?

[Author]

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