Mental Math (Addition)
Find the sum using mental math:
43 + 4
What is:
40 + 3 + 4 = 47
Find the difference using mental math:
52 - 9
What is:
53 - 10 (Add 1 to each number)
53 - 10 = 43
Which of the following ways shows how to estimate the sum of 365 + 212 by rounding to the nearest ten?
A) 300 + 200
B) 370 +210
C) 360 + 210
D) 400 + 200
What is:
B) 370 + 210
Which of the following ways shows how to estimate the sum of 542 - 408 by rounding to the nearest ten?
A) 500 - 400
B) 500 - 410
C) 540 - 410
D) 540 + 410
What is:
C) 540 - 410
Find the sum using mental math:
50 + 42
What is:
50 + 40 + 2 = 92
Find the difference using mental math:
28 - 19
What is:
29 - 20 (Add 1 to each number)
29 - 20 = 9
Round to the nearest ten to estimate:
18 + 43
What is:
20 + 40 = 60
Round to the nearest ten to estimate:
86 - 38
What is:
90 - 40 = 50
Find the sum using mental math:
35 + 26
What is:
35 + 20 + 6 = 61
or
35 + 20 + 5 + 1 = 61
Find the difference using mental math:
31 - 5
What is:
30 - 4 (Take 1 away from each number)
30 - 4 = 26
Round to the nearest hundred to estimate:
403 + 179
What is:
400 + 200 = 600
Round to the nearest hundred to estimate:
286 - 175
What is:
300 - 200 = 100
Find the sum using mental math:
5 + 38
What is:
5 + 30 + 8 = 43
or
5 + 30 + 5 + 3 = 43
Find the difference using mental math:
97 - 14
What is:
100 - 17 (Add 3 to each number)
100 - 17 = 83
Alex bought 118 Pokemon cards. His sister gave him 79 more. About how many Pokemon cards does Alex have now? Round to the nearest ten to estimate.
What is:
120 + 80 = 200
Jen drove 256 miles last week. This week she drove 532 miles. About how many more miles did Jen drive this week compared to last week? Find by rounding to the nearest ten.
What is:
530 - 260 = 270
Find the sum using mental math:
71 + 14
What is:
70 + 1 + 10 + 4 = 85
or
70 + 10 + 5 = 85
Find the difference using mental math:
73 - 39
What is:
74 - 40 (Add 1 to each number)
74 - 40 = 34
Use compatible numbers to estimate:
539 + 399
What is:
540 + 400 = 940
Use compatible numbers to estimate:
361 - 117
What is:
360 - 120 = 240