Make a Guess Calculator

A common issue teachers face in Algebra 1 and Geometry classes are student’s weak arithmetic skills.  Students tend to struggle with the simple rules of adding, subtracting, multiplying, and dividing integers. The teachers of these students are put in a difficult situation.   Do you spend class time practicing these basic skills before you go on to more advanced mathematical topics?  What if this takes weeks or months?   What if it is only half of your students who are struggling with the basic arithmetic?  How can students solve for x is they don’t know if 2 – 9 is positive, negative, 7, or 11?   Students get so many rules jumbled in their head that they will miss something as basic as 5 – 2.  One solution is to allow these students to use a calculator.  Which in my opinion, is a good way to allow weak students to attempt more advanced mathematics.  Now, as you probably know, there are a lot of people who don’t feel the same way.  I am not here to say which is the right solution, but rather, I have an idea that people on both sides of the calculator debate might find useful.

I created an calculator app for iOS devices.  It’s called Make a Guess a Calculator.   The basic idea is that it requires students to make a guess before they are given the answer. Here is how it works.

A student enters an expression into the calculator.  (I made it so students could see the entire expression that they entered.)


When they push the “=” button, a screen comes up asking students to make a guess. (The more I think about the question, “What is your guess?”, the less I like it. I almost feel like “What’s your answer?” or “What did you get?” might be better.) IMG_0927If a student has the right answer, then the calculator let’s them know they got it right.


If a student has the wrong answer, then the calculator gives the student a choice; they can choose to Try Again? or they can choose Give me the Answer.IMG_0928

If a student chooses Give me the Answer, they have to wait 3 seconds before the answer appears.  IMG_0929

The idea of the calculator is that students are trying the basic arithmetic on their own and the calculator is simply checking their work.   This calculator, in a way, hits both sides of the calculator debate.  Students can do more advanced topics because they have a calculator, but at the same time, they are practicing their basic arithmetic.    Now, I don’t think this is a perfect solution for students who struggle with basic arithmetic,  but I do feel it could be a better solution than what we do now.   I also think the calculator would help give students feedback with just basic arithmetic practice.  For example, if students were just using doing a worksheet with basic arithmetic they could check their answer as they go.

If you have ideas that you feel would make this calculator better, or ideas for students who struggle with arithmetic, I would love to hear them in the comments.

Here are some possible tweaks I am already thinking about.

1.  Have no timer.  For example, have students enter an expression, make guess, and then give them the answer.  I worry student will take advantage of this and not try the problem on their own first.

2.  Make the timer increase.   As a student get consecutive problems incorrect the timer would increase.  Now, the way around this would be to every time you get a problem wrong, just do a simple arithmetic problem such as 1+1 to reset the timer.

3.  Remove the timer and only give students the answer if they get it correct.

Screen Shot 2014-01-03 at 3.54.41 PM*There are a few quirks with the calculator.  The biggest issue has to do with fractions.   When you enter a fraction like 3/5, the answer is not 0.6, but rather, 0.   The reason is because of the way it is coded.   You are dividing an integer by an integer so your answer needs to be an integer.   If you enter 3.0/5 instead, then the calculator will give you 0.6.  My thoughts about this are I don’t really want the calculator to give the decimal answer anyways.   I feel more teacher would rather have the students find the reduced fraction answer.   For example, if a students enters 6/10 the correct answer that the calculator would check would be 3/5. This also makes more sense for fractions like 2/6.   If a student did 2/6 on the calculator, it is only going to tell them they are correct if they put the right number of 3s in their answer.   Now, I am not sure how hard this is to code and it probably brings in other issues,(For example, what is the answer if a student enters 2.4 + (1/2)?  Is it is 2.9 or 29/10?) but I do feel it would make more sense for this calculator.


One thought on “Make a Guess Calculator

  1. Nice ideas here, Sam. Have you seen the QAM calculator? It does a similar thing in requiring a guess, but yours also requires the payment of time to get the right answer.

    Neat stuff on your blog – your post on gamification shares an interesting approach to managing the intangibles that we value but don’t want to include as points for a grade.

    Thanks for sharing!


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