# CountFast 9 Home Activities

### OVERVIEW & PURPOSE

Week 5 of the 3rd Grade CountFast program focuses on strategies to add, subtract, and multiply with the digit 9. Â Spend 15 minutes each day on one of the activities listed in this module. Â 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.

#### EDUCATION STANDARDS

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.

#### OBJECTIVES

1. Mentally add and subtract with the number nine.
2. Mentally multiply one and two-digit numbers by nine.
DAY 1:Today, your child learned how to quickly add 9 to any number by thinking of the number 9 as being the same thing as 10 â€“ 1. Â To add nine quickly, first add 10 to the original number, and then back up one number. Â For example, to add 18 + 9, first realize that 18 + 10 is 28, then back up one spot on the number line, which would be 27 for a final answer. Â Practice with your child using the yellow cards. Â You can use the time record card to keep track of how quickly your child can add all of the yellow cards each round of practice.DAY 2:

Use the same procedure as yesterday. Â This time, your child will use the blue cards in the deck to practice subtracting 9 from any number. Â Using the idea that 9 is the same thing as 10 â€“ 1, first subtract 10 from the original number, and then go back up one number for the final answer. Â For example, solve 23 â€“ 9 by first subtracting 10. Â This puts you at 13. Â Then move up (in a positive direction) on the number line one spot, which gives the final answer of 24. Â Practice with your child using the blue cards. Â Record the speed your child completes the blue cards each round of practice.

DAY 3:

Today, we learned a neat trick using our fingers to quickly find the answer to any single-digit number times 9. Â Holding both hands up in front of you, think about â€˜readingâ€™ the fingers as 1 through 10, going from left to right. Â Hold down the finger that 9 is being multiplied by â€“ for example, 9 X 3 â€“ hold down the third finger. Â The fingers on the left of the one held down represent the â€˜tensâ€™ number of the answer. Â The fingers on the right represent the â€˜onesâ€™ digit of the answer. Â For 9 X 3, there are 2 fingers on the left, and 7 on the right, giving the answer of 27. Â Have your child model the technique for you. Â Then quickly ask your child various â€˜9 timesâ€™ facts to see how quickly he/she can get the answer using this method.

DAY 4:

Today your child learned a strategy to multiply two-digit numbers by 9. Â Â The quick way to mentally multiply by 9 is to multiply the original number by 10 (by simply adding a zero to the original number) and then subtract the original number to get the final answer. Â For example, 15 X 9 is solved quickly by first multiplying 15 X 10 to get 150, and then subtracting 15 from 150 to get a final answer of 135. Â Practice this method with your child using the green cards in the deck. Â Record your childâ€™s speed through the cards each round of practice.

DAY 5:

Today we reviewed all of the strategies for the number 9. Â Shuffle the deck and show your child one problem at a time. The addition, subtraction, and multiplication problems will be randomly scattered when shuffled â€“ so your child will have to pay careful attention to the type of problem on the card in order to choose the right strategy for solving. Â Make it a family game by having multiple members of the family race to answer correctly first!