Properties of Addition
In order to add 37 + 5 + 25, Kate adds 15 + 25 first. This is an example of which property?
Associative Property
Round to the nearest tenth: 3.45
3.5
Estimate using rounding:
123 + 57 =
120 + 60 = 180
3.25 + 5.32
8.57
Adam buys 3 football jerseys for $20 dollars each. How much did he spend in total?
$60
In order to add 80 + 19 + 20, Waite adds 80 + 20 first. This is an example of which property?
Commutative Property
Round to the nearest hundredth: 6.231
6.23
Estimate using rounding:
5,238 - 634 =
5,200 - 600 = 4,600
10.45 - 3.23 =
7.22
Abram bought a CD for $13 and a two DVD for $16. How much did he spend in total?
$45
Name the property:
14 + 7 + 0 = 14 + 7
Identity Property
Round to the nearest hundredth: 15.268
15.27
Estimate using rounding:
1.278 + 2.24
1 + 2 = 3
27.134 + 2.36 =
29.494
In 1979, Cathy's Coffee had 635 employees. Twenty years later, in 1999, the company had 927 employees. What is an estimate for the difference between the number of employees the company had in 1979 and 1999?
About 300 employees
Use compensation (adjusting numbers) to solve:
115 + 48 =
115 + 50 = 165
165 - 2 = 163
Round to the nearest thousandth: 159.2385
159.239
Estimate using rounding: 1,245.29 + 25 =
1,250 + 30 = 1,280
17 - 3.56 =
13.44
There were 378 students from the fourth, fifth, and sixth grades on a field trip. There were 109 students from the fourth grade and 113 students from the fifth grade. How many students were there from the sixth grade?
156 students
Explain the meaning of compatible numbers and give an example.
Compatible numbers are numbers that are easy to compute with mentally.
Ex: Making ten
Round to the nearest thousand: 1,209.2376
1,000
Estimate using rounding:
17,234.823 - 5.8
17,235 - 6 = 17,229
102.34 - 35.1 =
67.24
Cece brought $75 to the amusement park. She paid $30 for admission and $28 for food. How much money did she have left?
Draw a picture to represent the problem.
Teacher answer