…or cool down, or any time a teacher wants to get students working mental math.

Number strings are short mental math activities designed so that students work several calculations **in their head** then provide the answer in chorus, either verbally, with whiteboards, fingers or pencil and paper. Have students write their answer on their personal whiteboard and place it upside down on their desks. (To avoid excessive drawing, remind students that you want to hear their marker “click”.)

When directed, students will show their answer to the teacher, who immediately checks for comprehension and enthusiastically provides an answer to each student (“I challenge your answer” or “Yes!”).

In addition to providing a teacher with instant formative assessment, number strings offer the opportunity to integrate mathematics throughout the curriculum. Use the following samples or write your own!

First Grade:

Begin with the number of legs on a cat. (4)

Add the number of wheels on a bicycle (4 + 2 = 6)

Subtract the number of teachers in the classroom right now (6 – ?)

When I say: “Show me the answer”, I want you to raise the same number of fingers in the air as your answer.

“Are you ready? Show me the answer!”

Second Grade:

Start with the number of halves in a whole. (2)

Triple that number. (2 x 3 = 6)

Add the number of sides on a rectangle (6 + 4 = 10)

Write your answer on your whiteboard and flip it upside down. Hold it high over your head when I say: “Show me the answer!”

Third Grade:

Begin with the number of legs on an ant. (6)

Multiply by the number of legs on a spider. (6 x 8 = 48)

Divide by the number of legs on a human. (48 ÷ 2 = 24)

Subtract the number of legs on a horse. (24 – 4 = 20)

Sixth Grade:

Begin with the number of days in a leap year. (366)

Subtract the number of months in a year. (366 – 12 = 354)

Subtract the number of days in May. (354 – 30 = 324)

Add the number of days in a week. (324 + 7 = 331)

[…] the post about Number Strings, I referred to a student’s “personal whiteboard”. I use whiteboards throughout […]