Mental Math: Find Sums and Differences
6,200 - 829
5,371
Estimate the sum by rounding to the nearest thousand first: 4,868 + 1,185 = ?
4,868 + 1,185 = 5,000 + 1,000 = 6,000
Find the sum: 27,711 + 24,871
27,711 + 24,871 = 52,582
Find the difference: 98,567 - 69,474
98,567 - 69,474 = 29,093
Find the difference 3,904 - 3,427
3,904 - 3,427 = 477
8,800 + 2,180
10,980
Estimate the difference by rounding to the nearest thousand first then subtracting: 66,837 - 35,424
66,837 - 35,424 = 67,000 - 35,000 = 32,000
20,050 + 19,157 = 39,207
Find the difference: 834,726 - 743,612
834,726 - 743,612 = 91,114
Find the difference: 85,000 - 66,581
85,000 - 66,581 = 18,419
The town of Pine Grove collected 7,255 spirals and 20,782 pencils for a school supplies drive. The goal is 30,000 total spirals and pencils. Which answer choice shows the correct counting on strategy to find how many more spirals and pencils are needed to reach the goal?
(Please see Jeopardy Game slides for answer choices)
D)
The table shows the number of students at four different schools in the district. Estimate the total number of students at Johnson Elementary and Anderson Charter. Round each number to the nearest hundred then add.
(please see jeopardy google slides visual for chart)
2,827 + 1,161 = 2,800 + 1,200 = 4,000
Find the sum: 6,666 + 9,322
6,666 + 9,322 = 15,988
Find the difference: 37,426 - 20,133
37,426 - 20,133 = 17,293
Find the difference: 848,009 - 666,526
848,009 - 666,526 = 181,483
Is 83,300 - 23,546 greater than or less than 60,000? Explain how you can tell using mental math. Fill in the blanks:
One way to compare 83,300 - 23,546 to 60,000 is to find the [sum, difference] of 23,546 and 60,000. That number is [_______] which is [greater, less] than 83,300. So 83,300 - 23,546 is [greater, less] than 60,000.
One way to compare 83,300 - 23,546 to 60,000 is to find the [sum] of 23,546 and 60,000. That number is [ 83,546 ] which is [greater] than 83,300. So 83,300 - 23,546 is [less] than 60,000.
Sarah says, "When rounding to the nearest hundred, 612,111 rounds to 612,000" Do you agree? Explain.
You should not agree with Sarah because 612,111 rounds to 612,100 when rounded to the nearest hundred.
Find the sum: 19,642 + 13,966 + 8,627
19,642 + 13,966 + 8,627 = 42,235
A marker company makes 88,756 green markers, 13,812 blue markers, and 51,836 red markers. How many more green markers are made than blue and red markers combined?
green - (blue + red) = ans : 88,756 - (13,812 + 51,836) = 23,108
23,105 - 20,392 = 2,713
Owen solves a subtraction problem. First he uses the Associative Property to group 5,709 and 3,709 together. Then he subtracts their differences from 18,724. Do you agree with owen's reasoning? explain.
(please see jeopardy visual slides for answer choices)
C) No. Owen cannot change the groupings of numbers to subtract. He should use counting on instead
Suppose you want to estimate the sum of 10,314 and 10,383. Will rounding each number to the nearest hundred give an answer closer to the actual sum than rounding to the nearest ten? explain
Rounding to the nearest ten will give the closest answer to the actual sum because the smaller the place value position, the less the number changes when rounded.
Find the sum: 74,562 + 26,262 + 397,727
74,562 + 26,262 + 397,727 = 498,551
What is the inverse operation equation that can be used to check the answer for 44,678 - 22,728? (you need to tell me the addition equation for your check strategy)
21,950 + 22,728 = 44,678
Find the difference: 60,600 - 58,537
60,600 - 58,537 = 2,063