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
Use mental math to find the product. 9 × 62
558
200
A box of pens holds 196 pens. There are 6 full boxes of pens in the school supply room. What is the best estimate of pens?
1200 pens
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
Which is the same as 7 × 57?
A) 35 + 49
B) 350 + 49
C) 350 + 490
D) 7 + 57
B
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
What partial products will help you find the product 4 × 205?
A) 4 × 20 and 4 × 5
B) 4 × 200 and 4 × 50
C) 4 × 2 and 4 × 50
D) 4 × 200 and 4 × 5
D
400
A school has 6 fourth-grade classrooms and each classroom has 28 students. What is the best estimate of how many students there are?
About 180 students
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
What equation does this represent? 
8 X100= 800
500
Michelle wrote a whole number ending in 4 zeros. If she multiplies the number by 10, how many zeros should be in the product?
5
500
Which addition sentence shows how to use partial products to find 2 × 28?
A) 40 + 16 = 56
B) 16 + 4 = 20
C) 32 + 2 = 34
D) 40 + 8 = 48
A) 40 + 16= 56
500
Which will cost less than $4,000?
A) 6 rugs for $900 each
B) 8 rugs for $600 each
C) 7 rugs for $700 each
D) 9 rugs for $400 each
D
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