2.2. Multiply by 2-Digit Numbers. Unlock the Problem. Math Talk. Essential Question. Name. Module 2 61

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1 ? Name 2.2 Essential Question Multiply by 2-Digit Numbers How do you multiply by 2-digit numbers? Number and Operations 5.3.B Also 5.3.A MATHEMATICAL PROCESSES 5.1.B, 5.1.D Unlock the Problem A Siberian tiger sleeps as much as 18 hours a day, or 126 hours per week. About how many hours does a tiger sleep in a year? There are 52 weeks in one year. Use place value and regrouping. STEP 1 Estimate: Think: = STEP 2 Multiply by the ones STEP 3 Multiply by the tens ones = ones Math Talk Mathematical Processes Are there different numbers you could have used in Step 1 to find an estimate that is closer to the actual answer? Explain tens = tens, or ones STEP 4 Add the partial products So, a Siberian tiger sleeps about hours in one year. Remember Use patterns of zeros to find the product of multiples of = = = 1, = 1, = 12,000 Module 2 61

2 Share and Show Complete to find the product. 6 4 x _ 64 _ x _ 571 _ Estimate. Then find the product. 3. Estimate: 4. Estimate: 5. Estimate: Problem Solving Practice: Copy and Solve Estimate. Then find the product When you multiply 235 and 4 tens in , why does its product have a zero in the ones place? Explain. 15. Write Math Communicate How is multiplying a number by a 2-digit number similar to multiplying the number by a 1-digit number? How is it different? 62

3 Name Problem Solving Use the table for How much sleep does a jaguar get in 1 year? 17. Multi-Step In 1 year, how many more hours of sleep does a giant armadillo get than a platypus? Animal Animal Sleep Amounts Amount (usual hours per week) Jaguar 77 Giant Armadillo 127 Owl Monkey 119 Platypus 98 Three-Toed Sloth Multi-Step Owl monkeys sleep during the day, waking about 15 minutes after sundown to find food. At midnight, they rest for an hour or two, then continue to feed until sunrise. How many hours are owl monkeys awake in 1 year? Write Math Show Your Work 19. Three-toed sloths move very slowly, using as little energy as possible. They sleep, eat, and even give birth upside down. A baby sloth may cling to its mother for as much as 36 weeks after being born. How much of that time is the sloth asleep? 20. A tiger can eat as much as 40 pounds of food at a time, but it may go for several days without eating anything. Suppose a Siberian tiger in the wild eats an average of 18 pounds of food per day. How much food will the tiger eat in 28 days if he eats that amount each day? 21. Multi-Step Tickets to a museum cost $17 each. For a field trip, the museum offers a $4 discount on each ticket. How much will tickets for 32 students cost? Module 2 Lesson 2 63

4 Daily Assessment Task Mathematical Processes Fill in the bubble completely to show your answer. 22. In a locker, you find the ultimate puzzle book with 385 pages. There is also a clue leading you to another locker. Multiply the number of pages by 23 to get the code for the next locker. What is the code? A 7,755 B 6,545 C 1,925 D 8, Which estimate will help you solve this multiplication problem? = A B C D Multi-Step Charlie worked 45 hours this week. He earned $12 per hour. If he spent $134 for a new bicycle, how much money does he have left? A $383 B $406 C $414 D $674 TEXAS Test Prep A sloth s maximum speed on the ground is 15 feet in 1 minute. Even though it would be unlikely for a sloth to stay in motion for more than a few moments, how far would a sloth travel in 45 minutes at that speed? A B C D 270 feet 60 feet 675 feet 6,750 feet

5 Homework and Practice Name Number and Operations 5.3.B Also, 5.3.A MATHEMATICAL PROCESSES 5.1.B, 5.1.D 2.2 Multiply by 2-Digit Numbers Estimate. Then find the product Problem Solving 13. A male lion needs as much as 15 pounds of food each day, or 105 pounds of food each week. How much food does a lion need in one year? There are 52 weeks in one year. 14. An African elephant in the wild will eat for as long as 16 hours each day. For how many hours does an elephant eat in one year? There are 365 days in one year. Module 2 Lesson 2 65

6 Lesson Check TEXAS Test Prep Fill in the bubble completely to show your answer. 15. During the school year, Luis fills 138 pages of a composition notebook. There is a clue on the last page of the notebook. It says to multiply the number of pages in the book that were filled by 17. This is the code for a free prize in the lunchroom. What is the code? A 2,432 B 1,240 C 2,346 D 2, To train for a race, Jesse rode his bike for 48 minutes every day for 17 days. He estimates that he rode his bike for about 400 minutes in all. Which of the following statements is true? A B C D Jesse estimated correctly. Jesse rode his bike for about 1,000 minutes. Jesse rode his bike for about 70 minutes. Jesse rode his bike for about 500 minutes. 17. Marcus builds a brick wall that is 23 bricks across and 130 bricks high. Which is the best estimate of about how many bricks Marcus will use to build the wall? A 2,000 B 4,500 C 1,000 D 3, The parents club buys 12 cartons of pretzels to sell as refreshments at a soccer game. There are 75 bags of pretzels in one carton. How many bags of pretzels do the parents have? A 860 B 830 C 900 D Multi-Step Marli worked 37 hours this week. She earned $15 per hour. She spent $62 on a birthday gift for her sister. How much money does Marli have left? 66 A $464 B $493 C $378 D $ Multi-Step A farmer plants a field that can fit 27 rows of pepper plants with 14 plants in each row. She can also fit 4 rows of pumpkins with 4 plants in each row. How many plants can the farmer fit in her field? A 378 B 394 C 6,048 D 1,512