Multiply by 10, 100, and 1,000. Give your child a multiplication expression, and have him tell you the product (answer). For example, 3 × 10 = 30; 3 × 100 = 300; 3 × 1,000 = 3,000; 50 × 10 = 500; 50 × 100 = 5,000; 50 × 1,000 = 50,000
Quiz your child on the difference between a sum and a product. Try to do simple mental math together involving both sums and products. For example, tell your child, “Think of the product of 2 and 3.” (The answer is 6.) “Now think of the product of 3 and 4.” (The answer is 12.) “What’s the sum of those two products, 6 and 12?” (The answer is 18.)
Practice using partial products while doing multiplication. This can be a two-person activity with you and your child. Use easier three-digit numbers. For example, try 300 × 120. Tell your child, “You figure out 300 × 100, and I’ll figure out 300 × 20. Then we can add those two numbers together to get the result.” (300 × 100 = 30,000; 300 × 20 = 6,000; 30,000 + 6,000 = 36,000)
Help your child practice multiplication facts. Have him bounce a basketball as he says the multiples of different numbers. For example, he can practice saying the multiples of 8 with each bounce: 0, 8, 16, 24, 32, 40, 48, 56, 64, 72, 80. Then he can say them backward: 80, 72, 64, 56, 48, 40, 32, 24, 16, 8, 0.
Practice estimation at the grocery store. For example, say, “I want to buy 7 watermelons, and each one costs $2.99. Estimate my total cost.” (7 × $2.99 ≈ 7 × $3 = $21)
Play a skip-counting contest with your child. For example, count by 3’s to 30: 3, 6, 9, 12, 15, .... Count by 30’s to 300: 30, 60, 90, 120, 150, .... Count by 300’s to 3,000: 300, 600, 900, 1200, 1500, ....
Play the Divide the Card number game with your child: 1. Take out the jacks, queens, kings, and jokers; 2. Put the stack of remaining cards face down; 3. Flip three or four cards from the top of the deck, and place them face up on the table. The three- or four-digit number shown by these cards will represent the whole; 4. Your child flips two cards from the top of the deck and places them face up on the table. The two-digit number shown by these cards will represent the divisor; 5. Write the division expression using the whole and the divisor. Then ask your child to estimate the quotient; 6. Your child then solves the division problem using the standard algorithm. For example, you flip three cards with the numbers 3, 1, and 2; it represents 312. Your child flips two cards with the numbers 5 and 1; it represents 51. You write 312 ÷ 51 and say, “Estimate how many times 51 can go into 312.” She says, “Six,” and then solves the division problem using the standard algorithm. (The answer is 6 with a remainder of 6.)
Play the Multiply the Dice number game with your child to practice multi-digit multiplication. You can use two dice for two-digit numbers, three dice for three-digit numbers, or four dice for four-digit numbers: 1. You can select up to four dice to roll to create a multi-digit number; 2. Your child can select up to three dice to roll to create another multi-digit number; 3. You write the multiplication expression using the two numbers and say, “First, estimate the answer, and then solve the problem.” For example, you roll a 6, a 2, and a 5, which represents 625. She rolls a 1 and a 3, which represent 13. You write 625 × 13 and say, “First, estimate the answer, and then solve the problem.” Answers: 625 × 13 ≈ 600 × 10 = 6,000; 625 × 13 = 8,125 Challenge: Change the whole numbers of the first number rolled into a decimal number (e.g., 62.5 × 13, 6.25 × 13, or 0.625 × 13). Answers: 62.5 × 13 ≈ 60 × 10 = 600; 62.5 × 13 = 812.5; 6.25 × 13 ≈ 6 × 10 = 60; 6.25 × 13 = 81.25; 0.625 × 13 ≈ 1 × 10 = 10; 0.625 × 13 = 8.125