There’s Always Time for Estimating and Plenty of Resources

  • There’s Always Time for Estimating and Plenty of Resources

    By Jen McAleer, posted June 19, 2017—

    When estimation tasks are missing from the classroom, the most common excuse I hear is “I don’t have the time.” Many teachers feel the pressure of state-mandated tests and are often given timelines when certain topics should be introduced and, more important, finished. As a result, many “fun” or “engaging” activities that require time (like estimation) get pushed to the side. In this post, I will introduce you to a variety of easy-to-access resources on estimation and show just how valuable these tasks can be.

    My first go-to resource is Andrew Stadel’s Estimation 180. This website provides 220 days of tasks that can be used for classroom estimation. The tasks tend to play off one another, and the estimation you do one day can continue to the next. The most important element in the process is to encourage students to explain their thinking and not just say “I guessed.” Stadel also has a Google Form to submit your estimate and then look at how everyone has approached the problem.

    Tracy Johnston Zager blogs at Becoming the Math Teacher You Wish You'd Had and is another good resource. Zager mentioned one example in which students estimate the angles of various shapes and are then asked to prove or justify their estimates by using power polygons. Zager also incorporates estimation into her lessons by embedding it directly into problems that students are doing. For example, she showed her students 6739/47 and gathered student estimates, pasted them on the board, and discussed how reasonable (or unreasonable) each estimate was.

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    The students were given the prompt “I think ____ is unreasonable because ________” when framing the discussion. I have used this activity in my discussions of estimation, and it is a game changer.

    Another site that has inspired me to think outside the estimation box is Dane Ehlert’s When Math Happens. Ehlert does a fantastic job of taking content-level material and providing visuals. My students are engaged during these tasks on such topics as “Where will the two parabolas meet?” Ehlert has inspired me to work on my own creations.

    Another good site is Which has many tasks with embedded estimation. These ideas can start deeper conversations about multiplication, division, decimals, and percentages, all while questioning and looking more closely at the food and deals we consume daily.

    Estimation tasks need not be about perfection. I lose many students to the idea that mathematics has to be perfect. It is inefficient to be perfect while estimating because there are too many mathematical factors to consider. Students need to realize that they can be quite precise with just a few calculations.

    Check out some of the resources discussed here and follow @estimation180 and #MTBoS on Twitter. New resources are posted every day. Try a few out! You will soon be devising your own tasks once you see how engaged your students are.


    Jen McAleer is the head of middle school mathematics (grades 6–­8) at the Carroll School in Lincoln, Massachusetts. The Carroll School serves students with language-based learning difficulties who also tend to struggle with mathematics. McAleer has been teaching middle school for ten years and has a passion for giving all students a voice in mathematics and providing them with opportunities to be and feel successful while working with higher-level content, despite their struggles with procedures and computation. Reach McAleer via Twitter at @jennifuhs4.