Breaking Apart to Multiply (Distributive Property)
Estimate Products by Rounding
Reasonableness
100
1 x 100
100
100
9 x 20
180
100
Use the break apart method to multiply 5 x 14
(5 x 10) + (5 x 4)
50 + 20
70
100
Estimate the product-- 313 x 4
300 x 4 = 1,200
100
The Parkville Petting Zoo has 6 exhibits with 17 animals in each exhibit. What is a reasonable estimate for the number of animals in the whole petting zoo?
120 because 6 x 20 = 120
200
10 x 10
100
200
8 x 60
480
200
Use the break apart method to find 3 x 87
(3 x 80) + (3 x 7)
240 + 21
261
200
Estimate the product- 75 x 8
80 x 8 = 640
200
Susie's school has 4 grades with 47 students in each grade. What is a reasonable number of students in Susie's entire school?
200 because 4 x 50 = 200
300
100 x 100
10,000
300
7 x 800
5,600
300
Use the break apart method to multiply 4 x 53
(4 x 50) + (4 x 3)
200 + 12
212
300
Estimate the product- 91 x 7
90 x 7 = 630
300
Jane has 8 piles of rubber bands with 74 rubber bands in each pile. She says she has 1,399 rubber bands in all. Is her answer reasonable? Why or why not?
No it is not reasonable. 8 x 80 = about 640 rubber bands
400
100 x 10
1,000
400
60 x 70
4,200
400
Use the break apart method to multiply 9 x 28
(9 x 20) + (9 x 8)
180 + 72
252
400
Sam and Casey want to fly to Boston. One airline offers a round trip ticket for $361. About how much money will it cost the two boys to fly to Boston?
$400 x 2 = $800
400
Dawn's Spanish teacher ordered 20 Spanish CDs for her class. Each Spanish CD costs $9.50 Is Dawn's teacher reasonable when she says she will spend about $200? Why or why not?
Yes because 20 x $10 = $200
500
10 x 1,000
10,000
500
50 x 40
2,000
500
Use the break apart method to multiply 7 x 52
(7 x 50) + (7 x 2)
350 + 14
364
500
Mr. Hector's class walked 193 blocks in a Walk-A-Thon. They earned $4 for every block they walked. About how much money did they earn in all?
200 x $4 = $800
500
Karen is gluing sequins onto a T-shirt. She wants to make 5 rows with 34 sequins in each row. Karen says she thinks she will be using about 650 sequins. Is this reasonable? Why or why not?
No it is not reasonable. She is using 5 rows of about 30 sequins which is 150 sequins in all. This is much less than 650.