Math Flash Cards

CountFast 10


This module introduces a learning tool or trick to help students solve any number multiplied by 10, 100 or 1,000 very quickly using mental calculation.

After this module, the student will be able to use mental calculation to solve any number times 10, 100 and 1,000 very fast.


Week 6 of the 3rd Grade CountFast program focuses on strategies to multiply by powers of 10.  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 a sense of whole numbers and represent and use them in flexible ways, including relating, composing, and decomposing numbers
  2. Math.Content.3.OA.B.5
    Apply properties of operations as strategies to multiply and divide.


  1. Mentally multiply numbers by powers of 10.
  2. Mentally multiply numbers by powers of 100.


  1. One CountFast 10, 100 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.
  2. One writing utensil per student, optional per teacher plans.

CountFast 10, 100 Pack – Day 1

Teacher Model/Direct:  Use the yellow cards from the deck today to introduce the strategy of multiplying by 10.  The fast mental calculation is to simply add a zero to the number you are multiplying by 10.  If you are working with place value in math class, this is a great review of shifting places when multiplying.  Practice with the class by holding up one yellow card at a time.

Student Activity:  Give each student a deck and ask them to take out the yellow cards.  Working with a partner, take turns holding up the cards for the partner to multiply by 10 using the strategy from the lesson.  Be sure to send deck home with students for practice at home.

Home Activity: Students will take home the deck and the “CountFast Home Connection” letter.  Students will review the strategy for multiplying a number by 10.  Parents can record how quickly the child multiplies all of the yellow cards correctly.

CountFast 10, 100 Pack – Day 2

Teacher Model/Direct:  Using the same procedure as Day 1, introduce the blue cards in the deck.  Using the same concept of shifting place value, practice the quick mental strategy of multiplying any number times 100 by adding two zeros to the original number.  See how quickly the class can solve the blue cards as you hold them up.  For a challenge, see if students can predict what the strategy would be to multiply a number by 1,000 or 10,000, or 100,000…etc.

Student Activity:  Students should work with a partner, using the blue cards, to practice multiplying by 100.  If time allows, review the yellow cards and multiplying by 10.

Home Activity: Students will review the strategy for multiplying a number by 100.  Parents will use the blue cards with child and record how quickly the child answers all cards correctly each round.

CountFast 10, 100 Pack – Day 3

Teacher Model/Direct:  Use the pink cards from the deck.  Today, review with students the strategy to multiply any number by 10.  Then explain that if they can multiply by 10, they can also multiply by powers of 10 (20, 30, 40, etc.).  Since powers of 10 are the same as a number of copies of 10, we can quickly calculate a problem like 24 X 20 by first multiplying 24 X 2 copies, (getting 48), then multiplying that answer by 10 (add a zero to 48 to make 480).  Practice with the class by holding up the pick cards one at a time and reviewing the strategy.

Student Activity: With a partner, practice using the strategy to multiply by powers of 10 using the pink cards.

Home Activity: Students will practice multiplying by powers of 10 with parents using the pink cards.

CountFast 10, 100 – Day 4

Teacher Model/Direct: Use the green cards in the deck for today’s lesson.  Repeat the lesson plan from Day 3, this time using the same concept to multiply by powers of 100 (200, 300, 400, etc.).  Since 400 is the same as 4 copies of 100, demonstrate that students can quickly calculate the problem 5 X 400 by first multiplying the 5 X 4 to get 20, and then multiplying by 100 by simply adding two zeros to the answer (2000).  Practice this strategy with the class using each of the green cards.

Student Activity:  Students will work with partner using green cards to use the lesson strategy to multiply by powers of 100.  If time allows, review the other cards from previous lessons this week.

Home Activity:  Students will share and practice the strategy for multiplying by powers of 100 with parents.  Parents can track the speed in which the child works through all of the green cards each round of practice.

CountFast 10, 100 – Day 5

Teacher Model/Direct:  Today, review with students the strategies for multiplying by 10, 100, and powers of 10 and 100.  This can be made more challenging by shuffling all of the cards in the deck so that students learn to think quickly about what number they are multiplying by.

Student Activity:  With a partner, shuffle the deck and take turns answering the problems on the cards using the strategies for multiplying by 10 and 100.

Home Activity:  Students will review this week’s strategies for multiplying by 10 and 100.