1+1=3? Can it be? - Creating math riddles to show knowledge of curricular topics

Submitted by: Charyl Kerns Hills


1+1=3? Can It Be?


Grade level range:   3-4 but could easily be done with younger or older students

Length of time to teach lesson: 2 or 3 class sessions

Mentor text to be used in this lesson: 1+1=5 and Other Unlikely Additions- David LaRochelle & Brenda Sexton

Quick description of the lesson:  Students create math riddles to show knowledge of curricular topics. The writers are inspired by David LaRochelle & Brenda Sexton’s 1 + 1=5 and Other Unlikely Additions to write about their favorite interests or curricular topics. This activity is a great way to encourage writing across the curriculum. These riddles can be used to create a bulletin board display or class book.



Common Core Mathematical Practices Addressed in this Lesson:

          Make sense of problems and persevere in solving them.

              Students make conjectures about the form and meaning of the solution.    

              Students consider analogous problems.

          Reason abstractly.

              Students make sense of quantities and their relationships in problem



Writing Traits Addressed in this Lesson:

       Idea Development:

                        Putting researched ideas into one’s own words

       Word Choice:

                        Using precise nouns to assist the reader’s understanding

                        Incorporating interesting adjectives into the writing


                        Spelling skills


Objectives of this lesson:

 Students apply mathematical language with the structure of equations to show knowledge of topics.

Other than the mentor text, resources needed to teach this lesson:

 1+1 first page template

1+1 answer template

Colored pencils, markers, crayons

Text books and reference resources


Setting the Stage:

Early in the school year students were administered a fluency assessment of basic addition or multiplication facts to establish a baseline of their current understanding. Following the assessment students were asked to react to the following in their math journals:

Can 1+1=3? If no, give reasons why not; while if yes, give reasons why. Be ready to share your writing and thoughts.

Detailed step-by-step teaching instructions:

Students share thoughts regarding 1 + 1= 3. [Most students say no giving proof that 1 + 1=2 in a variety of ways.]

Then teacher instructs students to “to think out of the box.” Are there times when 1 + 1 can equal 5 or another number and not 2?

Read David LaRochelle & Brenda Sexton’s 1 + 1=5 and Other Unlikely Additions to the class. The right hand page presents the riddle with some subtle clues in the illustration.

Ex. 1 + 1= 7?

Students can respond orally to the riddle as a class or in pairs. For variety students also responded to some riddles in their math journal.

After some sharing of ideas, turn the page for the answer.

  1. 1 triangle + 1 square = 7 sides.

The book is read in its entirety to the class. Then students are asked to create their own math riddle or puzzle modeling the format of the shared book.

First students are asked to brainstorm interests and curricular topics in their math journal for ideas for their riddles. Students will come up with a variety of ideas: food, animals, bones, geography, etc.

Students star their favorite ideas and then narrow their idea to fit the math riddle format by creating their draft in their journal.

Another group session allows students to view the illustrations to view how the illustrator, Brenda Sexton, shares subtle clues through her drawings.

Students then draft their illustration for the riddle and then for the answer.

Students publish their work using the riddle and answer templates. It was great fun for each author to share their riddle with the class.






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