Math Flash Cards

Mental Subtraction (1-12)


This module continues to work on mental calculation. The previous card deck, Concept of + – (1-12) taught the concept and used physical movement of the cards and numbers.

This module continues to work on how to move the numbers in your mind without physical movement or counting with your fingers. In a sense it is making the brain work harder.

After this module the child will be able to “borrow” in their mind mentally. It will make the brain stronger and faster and continue to increase the confidence of the student.


Week eight of the 1st Grade CountFast program focuses on using repetition and quick calculation to create long-term memory of simple subtraction equations. This module includes equations to solve each day, with an emphasis on recording how long it takes each day to solve those equations correctly.  Spend 15 minutes each day on one of the activities listed in this module.  Card decks should go home with students each day for additional practice with a parent at home. Each week, a new deck is introduced and the previous deck is for the student to keep at home for continued practice.


1  NCTM Standard: develop fluency with basic number combinations for addition and subtraction

2  NCTM Standard: understand the effects of adding and subtracting whole numbers

3  CCSS.MATH.CONTENT.1.OA.C.6  Add and subtract within 20, demonstrating fluency for addition and subtraction within 10.


Develop fluency in solving simple subtraction equations.


One CountFast Mental Subtraction (1-12) card deck for each student.  This deck is for school and home use.  Discuss routine and expectations for taking home the deck and returning it to school each day.

One writing utensil per student

Mental Subtraction (1-12) – Day 1

Teacher Model/Direct:  Use the yellow cards from the deck.  These have subtraction equations on them.  Hold up one equation at a time for the class to read and answer together. (If you are holding the card, 9 – 8 =, the children should say “Nine minus (or take away) eight equals one.)  Practice together using all 10 yellow cards.  Then repeat the activity, telling students you will be going through the cards faster this time, and you only want them to say the answer (without reading aloud the problem).  Repeat this for 2-3 rounds as a whole group.

Student Activity:  Partner up students and give each pair one deck to work with.  Ask them to take out the yellow cards.  Students should take turns being the ‘card turner’ and the ‘solver’.  Have students practice positively encouraging one another, even when mistakes are made.  At the end of this activity, be sure to give each child a pack of the cards to take home for practice.

Home Activity: Students will take home the deck and the “CountFast Home Connection” letter.  Students will practice the subtraction equations on the yellow cards with parent(s).  Parents will time the child’s progress each round of play, using the YELLOW cards.

Mental Subtraction (1-12) – Day 2

Teacher Model/Direct:  Review the equations on the yellow cards with students, having them answer quickly as you hold up the cards.  Ask for a brave student volunteer to stand up and try to answer all of the cards on his/her own as you flip through the cards.  Demonstrate to the class how to time the student’s progress using a clock, watch, or sand timer.  When you say “GO”, begin flipping through the cards as fast as the student can accurately answer them.  After all 10 cards have been used, check the time to see how many seconds the student completed them in. (You can choose to have the student say the problem and the answer for each card, or to just give the answer.)  Explain to students that as they practice with a partner today, they will be using the BLUE cards in the pack and also practice timing each other.

Student Activity:  Repeat the activity from Day 1, using the BLUE cards in the deck.  Students should time each other’s progress in accurately completing the 10 cards and encourage each other to calculate a little faster each round.  You can have students keep track of their times on paper if you wish.

Home Activity: Students will play the subtraction equation game with parents and use the ‘Subtraction Time Record’ card to keep track of the child’s progress each round.

Mental Subtraction (1-12) – Day 3, 4, and 5

For days 3, 4, and 5, follow the lesson plan for Day 2 – but use the following color cards:

Day 3 – Pink cards

Day 4 – Green cards

Day 5 – Gold cards