## MSTAR Interventions

### Key Ideas

• Multiplication can be thought of as repeated addition, the joining of equal groups. (See Lesson 1.)
• Multiplication is equivalent to adding a number to itself a particular number of times. (See Lesson 1.)
• The equal sign means “equals” or “is equal to.” (See Lesson 2.)
• There are 2 ways to think about division: "How many groups?" or "How many in each group?" (See Lesson 3.)
• Division partitions a total into equal groups. (See Lesson 3.)
• The numbers in a skip-count sequence are called multiples. For example, when skip-counting by 10s, the numbers in the skip-count sequence—10, 20, 30, etc.—are multiples of 10. (See Lesson 4.)
• The products in a multiplication table are the multiples of the column or row number. (See Lesson 4.)
• Unknown facts can be found by taking apart or adding to known facts. (See Lessons 5 and 7.)
• Unknown facts can be derived from known facts, using the doubling strategy. (See Lessons 6 and 8.)
• Unknown facts can be found by taking apart or adding to a known fact. (See Lesson 7.)
• Multiplication and division are inverse operations. (See Lesson 9.)
• Given 3 x 5 = 15, by the commutative property of multiplication, 5 x 3 = 15. Because multiplication and division are inverse operations, 15 ÷ 5 = 3 and 15 ÷ 3 = 5. 3, 5, and 15 are a fact family. (See Lesson 10.)
• When multiplying a 1-digit number by multiples of 10, products end in 0. Find the product of the first factor and the digit in the tens place of the second factor and then add a 0. (See Lesson 11.)
• When multiplying a 1-digit number by multiples of 100, products end in two 0s. Find the product of the first factor and the digit in the hundreds place of the second factor and then add two 0s. (See Lesson 11.)
• When multiplying a 1-digit number by multiples of 1,000, products end in three 0s. Find the product of the first factor and the digit in the thousands place of the second factor and then add three 0s. (See Lesson 12.)
• When multiplying a 2-digit number by a 1-digit number, break apart the 2-digit number and multiply, using the distributive property. (See Lesson 12.)