Arrays and multiplying 2-Digit numbers by multiples of 10 Lesson 7-1 CCSS 4.NBT.5 Literature Link: Amanda Bean’s Amazing Dream by Cindy Neuschwander

MATH Essential Questions How can greater products be found mentally? MATH Essential Questions

MATH Essential Questions How can greater products be estimated? MATH Essential Questions

Warm up Complete the pattern. 14, 21, ___, ____, 42, 49, ___, ___, 70 9, ___, 15, 18, __, 24, 27, ___, 33, ___ 36, 48, ___, 72, ___, 96, ___, ___, 132, 144

VOCABULARY REVIEW equation product factors round Choose the best term from the words listed above to complete these sentences: 1. A(n) _________________ is another word for a number sentence. 2. One way to estimate a product is to _______________ each number. 3. A(n) ______________ is the answer to a multiplication problem. 4. In the equation 9x5 =45, 9 and 4 are both ___________________.

Today’s Lesson In this lesson, you will use place-value models and arrays to multiply two-digit numbers by 10 and by multiples of 10. Let’s look at the Envision Video for this lesson and take the quiz.

How can arrays help you multiply a 2 digit number by a multiple of 10? Think and write How can arrays help you multiply a 2 digit number by a multiple of 10?

Making arrays Array: A strategy used to solve a multiplication problem by drawing equal rows with an equal number of objects in each row. Example: For 3 X 4, make 3 rows with 4 objects per row.

Array practice – Use the grid paper to make the arrays Let’s review making arrays. Make an array to represent these problems and solve. 4 X 6 3 X 7 5 X 4 2 X 9

Making an array for larger problems 25 There are 10 teams in a baseball league. Each team has 25 players on the roster. One way to solve this problem is to make an array. How many teams are in the league? Draw the left side of the rectangle 10 units long. How many players are on each team (25). Draw the top of the rectangle 25 units long and complete the rectangle. 10 How would you find the answer to this problem?

Making larger arrays Let’s try this using a ruler & Grid Paper 20 To build an array for a larger problem like 15 X 20, make the left side of a rectangle 15 units long. This is also known as drawing a model. Then make the top of the rectangle 20 units long. Complete the remaining sides to complete your array. 15

Larger array practice Use the grid paper and a ruler Solve the following problems by making an array (drawing a model). 30 X 18 40 X 12 20 X 19

Problem 1 Make a model to solve Mrs. Tyrell has 20 tests to grade. Each test has 18 problems. How many problems will Mrs. Tyrell grade in all?

Problem 2 Make a model to solve There are 30 teams in the soccer league. Each team has 16 players on the roster. How many soccer players are there altogether in the league?

Problem 3 make a model to solve Chef John is making 40 pans of chicken. Each pan has 22 pieces of chicken. How many pieces of chicken does Chef John make in all?

Lesson Wrap Up In this lesson, you learned to use an array to find the product of a two-digit number and a multiple of 10. Reflection in Notebook: I think making an array helps with multiplication because…. Center Activity – Teamwork (7-1). Homework (7-1 Practice) for one “Paw Signature” and (7-1 Reaching & Practice) if you want two “Paw Signatures.” Website for Practice: Website for Practice: http://www.mathplayground.com/multiplication02.html