A lot of students struggle with more advanced mathematics because they lack basic arithmetic skills. Make a Guess Calculator allows students to practice these skills while they work on more advanced mathematical topics. With normal calculators, students are not required to try the problem on their own first. Make a Guess Calculator requires students to enter a guess before the calculator shows the answer.
More in this blog post from the developer.
6 March 2014 Edit: 2 July 2014