OVERVIEW & PURPOSE
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.
- NCTM Standard: develop a sense of whole numbers and represent and use them in flexible ways, including relating, composing, and decomposing numbers
Apply properties of operations as strategies to multiply and divide.
- Mentally multiply numbers by powers of 10.
- Mentally multiply numbers by powers of 100.
DAY 1:Today, your child learned how to quickly multiply any number by 10. The quick mental strategy is to simply add a zero to the original number. For example, multiply 23 X 10 by adding a zero to the 23 to get the answer of 230. Practice this strategy with your child by reviewing the yellow cards in the pack. If you wish, record how quickly your child can complete the yellow cards, and see if he/she can beat that time each round of play.
Use the same procedure as yesterday. This time, your child will use the blue cards in the deck to practice multiplying any number by 100. The quick mental strategy is to simply add two zeros to the original number. For example, multiply 46 X 100 by adding two zeros to the 46 to get the answer of 4600. Practice this strategy with your child by reviewing the blue cards in the deck together. Record how fast your child can get through the answers.
Expanding on what we learned in Days 1 and 2, today we practiced multiplying any number by a power of 10 (20, 30, 40, etc.). For example, the fast way to multiply 5 X 30 is to first multiply 5 X 3 to get 15, then add a zero to the answer to get 150. Similarly, 5 X 40 is solved by multiplying 5 X 4 to get 20, and then adding a zero to the answer for a total of 200. Practice this with your child using the pink cards in the deck and recording the time it takes your child to get through all of the problems.
Today we practiced multiplying any number by a power of 100 (200, 300, 400, etc.) using the same idea as practiced on Day 3. For example, the fast way to multiply 4 X 200 is to first multiply 4 X 2 to get 8, and then add two zeros to the answer to get 800. Practice this with your child using the green cards from the deck and recording the time it takes your child to get through all of the problems.
Today we reviewed all of the strategies for multiplying by 10, 100, and powers of those numbers. Shuffle the whole deck and practice multiplication with your child. Help your child set a realistic goal for how fast he/she can get through the whole deck. Time your child and celebrate together when the goal is met!