Multiplying 2 digit numbers by multiples of 10 Lesson 8-3 CCSS 4.NBT.5

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 Solve. 72 ÷ 8 54 ÷ 6 27 ÷ 3 42 ÷ 7

Think and write Why is it easy to multiply by multiples of ten?

Today’s Lesson In this lesson, you will use a grid to break apart numbers into tens and ones and solve simpler problems to help find the products. You will also use a pattern similar to when you were multiplying multiples of 10 and 100. Let’s look at the Envision Video for this lesson and take the quiz.

Multiplying with multiples of 10 There is a shortcut for multiplying numbers that end in zero. You can use the partial products method. Multiply 20 x 28. Step 1: Break 28 into tens and ones (20 + 8) Step 2: Multiply 20 x 20 = 400. Step 3: Multiply 20 x 8 = 160. Step 4: Add the partial products: 400 +160 = 560.

Practice! Use the partial products method to solve. 32 X 80 23 X 50

Problem 1 The aquarium has 84 octopuses. If each octopus weighs about 20 pounds, what would their combined weight be? Use the partial products method to solve.

Problem 2 There are 33 seals on the beach that weigh about 80 pounds each. How much would all of the seals weigh together? Use the partial products method to solve.

Problem 3 A giant squid is about 30 feet long. How long would 68 giant squids be in all? Use the partial products method to solve.

Problem 4 An average seahorse grows to be 14 in. long. How long would 40 seahorses be combined? Use partial products to solve.

Lesson Wrap Up In this lesson, you learned that you can use grids and patterns to multiply 2-digit numbers by multiples of 10. Reflection in Notebook: I would explain multiplying 2-Digit Numbers by Multiples of 10 to a friend by…. Center Activity – (8-3). Homework (8-3 Practice) for one “Paw Signature” and (8-3 Reaching & Practice) if you want two “Paw Signatures.” Website for Practice: Website for Practice: http://www.multiplication.com/games/all-games