Three-Digit Addition & Subtraction — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A store had 465 toys. They sold 187 in the morning and 134 in the afternoon. How many toys are left?
A) 134
B) 144
C) 154
D) 244
First add the toys sold: 187 + 134 = 321. Then subtract from the starting amount: 465 - 321 = 144 toys remaining.
2. What is the best estimate for 389 + 512 when both numbers are rounded to the nearest hundred?
A) 800
B) 900
C) 1000
D) 700
Rounded to the nearest hundred, 389 becomes 400 and 512 becomes 500. Adding those estimates gives 900, which is the closest reasonable total.
3. Sam has 723 baseball cards. He gives 258 to his friend and then gets 175 new ones. How many does he have now?
A) 540
B) 640
C) 650
D) 740
Start by subtracting the cards Sam gave away: 723 - 258 = 465. Then add the new cards: 465 + 175 = 640 baseball cards in all.
4. Which subtraction problem requires borrowing in both the ones and tens places?
A) 876 - 543
B) 654 - 278
C) 999 - 111
D) 735 - 214
In 654 - 278, the ones need borrowing because 4 is less than 8, and after borrowing the tens become 4 - 7, which also needs borrowing from the hundreds. The other choices either need no borrowing or only one regrouping.
Part B: Fill in the Blank
Write the correct answer on each line.
1. 347 + 286 + 158 = 791.
Add the first two numbers: 347 + 286 = 633. Then add the third: 633 + 158 = 791. Lining up place values and regrouping gives the same total.
2. A library has 925 books. If 368 are checked out, 557 books remain.
Subtracting the checked-out books from the total tells how many remain: 925 - 368 = 557. Borrowing is needed in the ones and tens columns.
3. 600 - 247 = 353.
Because 600 has zeros in the tens and ones, borrow across both to get 5-9-10 minus 2-4-7. That subtraction gives 353.
4. The sum of 489 and 376 is 865.
Adding the ones gives 9 + 6 = 15, write 5 carry 1. Tens: 8 + 7 + 1 = 16, write 6 carry 1. Hundreds: 4 + 3 + 1 = 8. The sum is 865.
5. 1000 - 637 = 363.
Subtracting from 1000 requires borrowing across all three zeros. After regrouping, you compute 9-9-10 minus 6-3-7, which leaves 363.