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MATH UNIT 7 4 th Grade. Arrays and Multiplying 2-Digit Numbers How can you multiply using an array? There are 13 trees in 24 equal rows. How many trees.

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Presentation on theme: "MATH UNIT 7 4 th Grade. Arrays and Multiplying 2-Digit Numbers How can you multiply using an array? There are 13 trees in 24 equal rows. How many trees."— Presentation transcript:

1 MATH UNIT 7 4 th Grade

2 Arrays and Multiplying 2-Digit Numbers How can you multiply using an array? There are 13 trees in 24 equal rows. How many trees are there? 10 x 20 3 x 20 3 x 4 4 x 10

3 What is another way to multiply 2-Digit numbers? Draw a table. Separate each factors into tens and ones. Multiply to find partial products. Add. 37 x

4 Find the product of 26 x 18 using partial products.

5 Find the product of 11 x 16 using partial products.

6 Use partial products to solve 19 x 27.

7 Complete the table to find the product. 18 x 25

8 Complete the tables to solve. 12 x 2817 x 6813 x x 2722 x 8818 x 25

9 The prices at Dunn’s Store are shown at the right. If 27 boxes of neon key chains and 35 boxes of glow-in-the-dark pens were purchased, what was the total cost? ItemPrice per box Neon key chains$16 Glow-in-the-dark pens$12

10 The Florida Theatre in Jacksonville has 1,918 seats in all. Section 200 has 27 rows with 14 seats in each row. How many seats are in Section 200? ? Seats in Section

11 Maggie is making a balloon game for the school fair. Kids will throw darts at a 13 x 14 display to try to pop the balloons. How many balloons are needed to set up the game?

12 Maggie knows that she will have to completely refill the balloon board at least 15 times during the day of the fair. Which expression shows how to find the number of balloons she will need? a.15 x 13 b. 15 x ( 13 x 14 ) c. 15 x 14 d. 15 x ( )

13 Megan has d customers in her dog walking service. She walks each dog once a day. Which expression shows how many dogs she walks in 12 weeks? a.( d + 12 ) x 7 b. 12 – ( d x 7 ) c. (d x 7 ) x 12 d. ( 7 x 12 ) + d

14 The flagpole in front of the school is 35 feet high. How many inches tall is the flagpole?

15 The Castillo de San Marcos is the Spanish fortress in old St. Augustine, Florida. I was built between 1672 and Rounded to the nearest ten thousand, how many pesos did it cost to build the fortress at that time? It cost 138,375 pesos to build this fortress.

16 Find all of the partial products and then add to find the product. 2 3 X X

17 Find all of the partial products and then add to find the product. 3 4 X X

18 Find all of the partial products and then add to find the product. 6 4 X X

19 A pair of one type of shoes weighs 15 ounces. The shoebox they come in weighs 2 ounces. Which is the total weight in ounces of 15 pairs of these shoes, including the boxes? a. 147 ouncesc. 225 ounces b. 155 ouncesd. 255 ounces

20 Nikie estimated 23 x 43 by using 20 x 40. Rebecca estimated 23 x 43 by using 25 x 40. Which method will give a closer estimate and why?

21 Runway 3 at the Airport is 13,000 feet long and Runway 5 is 9,472 feet long. How much shorter is Runway 5 than Runway 2?

22 Our school has two large patios. One is rectangular and is 24 feet long by 18 feet wide. The other is square and each side is 21 feet long. Which patio has the largest perimeter? Which patio has the largest area?

23 Mrs. B buys 23 rock identification kits for her science lessons. If each kit contains 28 rocks, how many rocks are there in all? Use the breaking apart method to solve.

24 Ryan’s class raised frogs from tadpoles. The class has 19students and each raised 6 tadpoles. All but 6 of the tadpoles grew to be frogs. Write a number sentence to show how many frogs the class has.

25 It took Sophie 45 minutes to clean her room. How many seconds did it take her to clean her room?

26 How many fossil kits with 12 samples each have the same number of fossils as 30 fossil kits with 8 samples each?

27 One family of Florida scrub jays inhabits about 25 acres of land. No other scrub jay families live within this area. How many acres of land do 24 families of Florida scrub jays need? Endangered species

28 A roller coaster runs rides 50 times an hour and reaches speeds of 70 miles per hour. Using the picture, how many people can ride each hour?

29 Multiplying 2-Digit by 2-Digit A ferry carried an average of 37 cars per trip on Saturday. If the ferry made 24 one-way trips, how many cars did it carry?

30 The Queen Mary 2’s height above the water is the same as a 23-story building. If a single story is 11 feet tall, how high above the water is the Queen Mary 2?

31 Alex bought sketch pads for all 23 students in his class. Each sketch pad contained 50 sheets of paper. How many sheets of paper were there all together?

32 In 2005, an ultra light airplane tracked Monarch butterflies migrating to Mexico. Over 13 days, how many miles did the butterflies travel? Average distance each day: 45 miles.

33 Two-Question Problems 1.Arianne and Autumn are preparing for a bike race. On Wednesday, they rode their bikes 32 miles in the morning and 22 miles in the afternoon. How many miles did they ride in all? 2.Arianne and Autumn biked the same number of miles on Wednesday, Thursday, Friday, and Saturday. How far did they ride during the week?

34 Charlie used 3 rolls of film to take pictures on vacation. There were 24pictures on each roll. How many pictures did Charlie take. Charlie had two copies made of each picture. How many copies were made?

35 Caroline buys a sandwich for $4, an apple for $1, and a drink for $2. How much did she pay in all? How much change did she receive if she paid with a $20 bill?

36 Ethan and Jimmy mow their neighbors’ lawns in the summer. Ethan mows 5 lawns each week. Jimmy mows three times as many lawns as Ethan. How many lawns does Jimmy mow each week? Jimmy gets paid $20 for each lawn he mows. How much does he get paid each week?

37 The Florida panther is known to sleep up to 18 hours each day. About how many ours would a Florida panther sleep in one month?

38 Billy’s mom brought 3 bags of plain popcorn and 2 bags of caramel popcorn to the park. How many bags of popcorn did Billy’s mom bring to the park? Each bag of popcorn contained 16 servings. How many servings of popcorn did Billy’s mom bring to the park?

39 Kay plans to retile her porch floor. She wants to buy 26 black tiles and 23 white tiles. Each tile costs $2. How much money will It cost Kay to retile her porch?

40 How can you multiply with multiples of 10, 100, and 1,000? The Ocean Water company produces water bottles. If it made 800 cases of water in one day, how many water bottles would it produce in all? 30bottles per case

41 To find the answer use the pattern: 8 x 30 = ___0 80 x 30 = ___ x 30 = ___,000 What if each case holds 50 bottles?

42 When multiplying by multiples of 10, 100, 1000, the product is the basic fact followed by the number of zeros in both factors. 400 x x 7006,000 x 5,000

43 The product is the basic fact followed by the number of zeros in both factors. 60 x 2, x 3007,000 x 3,000 40,000 x 2,000120,000 x 9,0008,000 x 6,000

44 The number of times that a heart beats each minute is called the heart rate. Smaller animals usually have higher heart rates than large animals. Find the heart beats per hour for each. ELEPHANT30 PIG70 RABBIT200 MOUSE600

45 A hummingbird’s heart can beat up to 1,260 times per minute. About how many times does it beat in 5 minutes?

46 The goal of Orange Street Elementary was to collect 16,000 soup labels. Did the school meet its goal if 20 classes collected 650 labels each? How many more or fewer labels than 16,000 did the school collect?

47 How many zeros will be in the product of 50,000 x 800,000? _________ How many zeros will be in the product of 900,000 x 90,000? _________

48 In one year a city recorded a total of 86 rainy days. How many days did it NOT rain during that year?

49 William has saved $82. He wants to buy a new ripstick that costs $163 and a helmet that costs $32. How much more will he need to save?

50 Estimation of Products In 1991, NASA launched the Upper Atmosphere Research Satellite (UARS). It orbits Earth about 105 times each week. There are 52 weeks in one year. About how many orbits does it make in one full year?

51 Use rounding to estimate the number of orbits in one year. 52 x x 100 = 5,200 or Use compatible numbers 52 x x 100 = 5,500 Remember: These are both ESTIMATES!

52 Solve by ESTIMATING! 324 x x x x x x x x x x X X 61

53 Solve by ESTIMATING! 198 X X X X X X X X X X X X 668

54 During one space mission, an American astronaut spent more than 236 hours in space. About how many minutes did he spend in space?


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