Estimating
Estimate the sum by rounding to the nearest hundred.
178 + 221 =
200 + 200 = 400
641 + 354 =
995
678 - 451 =
227
Johnny walked 127 feet on Monday. Then he walked 72 more feet on Tuesday. Lastly, he walked 341 feet on Wednesday. How far did Johnny walk over all three days?
540 feet
What is a Sum?
The answer to an addition problem.
Estimate the sum by rounding to the nearest ten.
65 + 113 =
70 + 110 = 180
369 + 428 =
797
640 - 212 =
428
Mrs. Yeniffer had 537 eggs. She sold 292 eggs to a bakery. How many eggs did Yeniffer have left?
245 eggs
What is a difference?
The answer to a subtraction problem.
Estimate the sum by rounding to the nearest ten.
684 + 159 =
680 + 160 = 840
83 + 595 =
678
748 - 469 =
279
Brandon spent $157 on a video game. He now has $129 in his bank account. How much money did he have to start with?
$286
What is an Estimate?
A number that is close to the exact number.
Estimate the difference by rounding to the nearest ten.
367 - 145 =
370 - 150 = 220
146 + 579 =
725
905 - 147 =
758
Janelle and Jarred bought 431 cards. They gave 105 cards to their friend. Then they bought 237 more cards. How many cards do they have now?
563 cards
Subtraction
Estimate the difference by rounding to the nearest ten.
713 - 469 =
710 - 470 = 240
679 + 227 =
906
812 - 317 =
495
Ms. Whelan's sniffling students use 188 tissues on Monday, 356 tissues on Tuesday, and 275 tissues on Wednesday. Ms. Whelan had 1,000 tissues at the beginning of the week. How many tissues are left?
188 + 356 + 275 = 819
1,000 - 819 = 181
Two operations that undo each other, such as addition and subtraction.
Inverse Operations