Arrays and Multiplying by 10 and 100
Multiplying by Multiples of 10 and 100's
Breaking apart to Multiply
Use Rounding to Estimate
Problem- solving : Reasonableness
100
A ) 6 + 4 = 10
B ) 4 × 6 = 24
C) 6 + 40 = 46
D) 6 × 40 = 240
4 X 6= 24
100
4x20
80
100
Break apart 3 x 24
3 x 20
3 x 4
100
Estimate 41 x 9
360
100
Isabelle has 9 ant farms. Each ant farm has 99 ants.
What is a reasonable estimate of how many ants Isabelle has?
900
200
Ambika has 4 sheets of stickers. There are 10 stickers on each sheet.
How many stickers does Ambika have?
40
200
3x600
1800
200
Each of the 109 fourth graders will need 3 notebooks this school year.
What is the total number of notebooks the fourth graders will need this year?
327 notebooks
200
What’s the best estimate of the product for the problem shown below?
987 × 6
What’s the best estimate of the product for the problem shown below?
987 × 6
200
Ursula has an album in which she keeps pressed flowers. The album has 34 pages, and each page has 7 pressed flowers.
Which of the following shows a reasonable estimate of how many pressed flowers Ursula has?
A) 30 × 7 = 210
B) 40 × 7 = 280
C) 50 × 5 = 250
D) 60 × 4 = 240
A
300
What equation shows the array above?
6 X 10= 60
300
Find the product of 50 and 7.
350
300
Mr. Sanchez gives 5 tours of the Grand Canyon each day. There are 12 people in every tour group. How many people go on one of Mr. Sanchez’s tours each day.
60
300
Which of these is the closest estimate for 6 × 68?
6 X 70= 420
300
Miriam can put 28 books on a shelf. What is the best estimate of the amount of books she can put on 8 shelves?
8 X 30= 240 books
400
Jan bought 5 bags of shells. There are 100 shells in each bag.
How many shells does Jan have?
500
400
Complete this statement. To find 3 × 800, multiply 3 and 8. Then write _____ zeros at the end.
2
400
C
400
The high school marching band has 339 band members. Each band member is asked to pay $8 for transportation. What is the best estimate expression can Tara use to get the best estimate of the amount of money collected to pay for band transportation?
300 x 8
400
A DVD cabinet has 7 shelves. Each shelf can hold about 38 DVDs.
What is a reasonable estimate of the number of DVDs the cabinet can hold?
A) 210 because 7 × 38 is about 7 × 30 = 210
B) 280 because 7 × 38 is about 7 × 40 = 280
C) 320 because 7 × 38 is about 8 × 40 = 320
D)350 because 7 × 38 is about 7 × 50 = 350
B
500
C
500
Cara added 20 pages of photos to her photo album. She put 6 photos on each page. How many photos she added to the album?
120
500
D
500
58 x 5
and
63 x 5
500
In Omar's school, there are 8 fourth-grade classrooms. Each classroom has about 22 students. Which is a reasonable estimate of the number of fourth graders in Omar's school?
A) 160 because 8 × 22 is about 8 × 20 = 160
B ) 180 because 8 × 22 is about 9 × 20 = 180
C ) 200 because 8 × 22 is about 8 × 25 = 200
D) 300 because 8 × 22 is about 10 × 30 = 300
A