Arrays
The dentist ordered 10 boxes of toothbrushes. There are 15 toothbrushes. How many toothbrushes did the dentist order?
150 toothbrushes
80 x 50=
4,000
38 x 13 rounds to...
40 x 10 = 400
Estimate: Use compatible numbers
32 x 24 =
30 x 25 = 750
16
There are 20 vases on the tables in a restaurant. If each vase has 8 flowers, how many flowers are there in the restaurant?
160 flowers
70 x 80 =
5,600
82 x 36 =
80 x 40 = 3,200
Estimate: Use compatible numbers
53 x 54
50 x 50 = 2,500
Scarlet has 18 pictures of birds. She has half as many pictures of trees as pictures of birds. She has 3 times as many pictures of flowers as trees. How many pictures of birds, trees, and flowers does Scarlet have?
54
34 x 10 =
340
2,400 words
Frankie used rounding to estimate the product of 45 x 42 and got 1,600. What did Frankie do wrong? What is the correct estimate?
Frankie rounded 45 down to 40 instead of up to 50.
50 x 40 = 2,000
Ashley swims about 55 minutes each day. Estimate the number of minutes she swims in 21 days.
60 x 20 = 1,200
Aspen is setting up chairs for a concert. One section will have 6 equal rows of 6 chairs each. The other section will have 8 equal rows of 2 chairs each. How many chairs will there be in all?
52 chairs
Henry used place-value blocks to model 20 x 15. He used 20 tens blocks. How many ones blocks did he use?
100
Each of the 90 fourth-grade students at North Elementary read 30 books over the school year. How many books did they read altogether?
2,700 books
Lilly is stacking 49 boxes of dictionaries on the school shelves. Each box weighs about 28 pounds. What is the best estimate of the total weight of the boxes?
50 x 30 = 1,500 pounds
About 1,500 pounds
Ms. Williams ordered 28 cartons of tape for a school projects. Each carton contained 24 rolls. What is the best estimate of the total number of rolls of tape ordered?
750 rolls of tape
A tennis pro has 12 cans of tennis balls. There are 3 balls in each can. He gives an equal number of balls to each of the 4 players. After the lesson, he realizes that each player lost 3 balls. How many tennis balls are left?
12 x 3 = 36 tennis balls
4 players x 3 lost tennis balls = 12 lost
36 - 12 = 24
There are 24 balls left.
The art teacher has 50 boxes of crayons with 16 crayons in each box. She gives 10 of the boxes to students to use. Explain how to find how many crayons she has left.
50 x 16 = 800
10 x 16 = 160
800 - 160 = 640
Margo claims that when she multiplied 90 x 40 she got an answer of 360. Is Margo correct? If not, what is the correct answer?
No Margo is not correct. The correct answer is 3,600.
It took Mrs. Ford about 22 hours to drive from her home in Florida to her new home in Missouri. She drove 65 miles each hour. What is the best way to estimate the distance from her home in Florida to her new home in Missouri?
20 x 70
Use estimated to show which has the greater product.
68 x 42 or 48 x 62
70 x 40 = 2,800
50 x 60 = 3,000
Fourteen students in Mr. Wilkes class have 2 pets. Three students have 1 pet. There are 3 students that have 4 pets. How many pets does the class have altogether?
14 x 2 = 28
3 x 1 = 3
3 x 4 = 12
28 + 3 + 12 = 43 total pets