Addition and subtraction with 3-digit numbers – Year 3 maths worksheet answers to download as PDF

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1. Answer to Question 1

   1. 346 + 30 = 376.
   2. 512 + 200 = 712.
   3. 278 + 5 = 283.
   4. 497 + 40 = 537.
   5. 605 + 95 = 700.

2. Answer to Question 2

   1. 578 − 40 = 538.
   2. 842 − 300 = 542.
   3. 463 − 7 = 456.
   4. 700 − 50 = 650.
   5. 305 − 9 = 296.

3. Answer to Question 3

   1. Ones: 3 + 5 = 8. Tens: 4 + 2 = 6. Hundreds: 2 + 1 = 3. Answer: 368.
   2. Ones: 7 + 4 = 11 (write 1, exchange 1 ten). Tens: 6 + 1 + 1 = 8. Hundreds: 3 + 2 = 5. Answer: 581.
   3. Ones: 8 + 6 = 14 (write 4, exchange 1 ten). Tens: 5 + 7 + 1 = 13 (write 3, exchange 1 hundred). Hundreds: 4 + 2 + 1 = 7. Answer: 734.
   4. Ones: 9 + 7 = 16 (write 6, exchange 1 ten). Tens: 8 + 5 + 1 = 14 (write 4, exchange 1 hundred). Hundreds: 3 + 4 + 1 = 8. Answer: 846.

4. Answer to Question 4

   1. Ones: 8 − 5 = 3. Tens: 6 − 4 = 2. Hundreds: 7 − 3 = 4. Answer: 423. Check: 423 + 345 = 768.
   2. Ones: exchange 1 ten for 10 ones: 13 − 8 = 5. Tens: exchange 1 hundred for 10 tens: 11 − 6 = 5. Hundreds: 4 − 1 = 3. Answer: 355. Check: 355 + 168 = 523.
   3. There are no tens, so exchange 1 hundred for 10 tens. Ones: exchange 1 ten for 10 ones: 12 − 7 = 5. Tens: 9 − 5 = 4. Hundreds: 7 − 4 = 3. Answer: 345. Check: 345 + 457 = 802.
   4. Ones: exchange 1 ten for 10 ones: 10 − 3 = 7. Tens: exchange 1 hundred for 10 tens: 13 − 8 = 5. Hundreds: 5 − 2 = 3. Answer: 357. Check: 357 + 283 = 640.

5. Answer to Question 5

   1. Estimate: 300 + 400 = 700. Exact: 298 + 405 = 703. The exact answer is close to the estimate.
   2. Estimate: 600 - 400 = 200. Exact: 612 - 389 = 223. The exact answer is close to the estimate.
   3. Estimate: 200 + 200 = 400. Exact: 187 + 214 = 401. The exact answer is close to the estimate.
   4. Estimate: 800 - 400 = 400. Exact: 796 - 408 = 388. The exact answer is close to the estimate.

6. Answer to Question 6

   1. 462 − 135 = 327. Check: 327 + 135 = 462.
   2. 651 − 280 = 371. Check: 280 + 371 = 651.
   3. 275 + 148 = 423. Check: 423 − 148 = 275.
   4. 704 − 329 = 375. Check: 704 − 375 = 329.

7. Answer to Question 7

   1. 248 + 319 = 567. Ones 8 + 9 = 17, tens 4 + 1 + 1 = 6, hundreds 2 + 3 = 5.
   2. 567 + 175 = 742.
   3. 800 − 742 = 58 eggs.
   4. 319 − 175 = 144.

8. Answer to Question 8

   1. Add the two coaches: 56 + 49. Adding 49 is adding 50 and taking 1 away: 56 + 50 = 106, then 106 − 1 = 105 children.
   2. Add the teachers and helpers: 105 + 38. 105 + 30 = 135, then 135 + 8 = 143 people.
   3. One free ticket covers a group of 100. 143 − 100 = 43 people are left over, not enough for a second free ticket.
   4. Coach B has 60 seats and 49 children. Count on from 49 to 60: 1 to reach 50, then 10 more. 11 seats are empty.

9. Answer to Question 9

   1. 215 − 128 = £87.
   2. 87 − 50 = £37.
   3. 37 − 25 = £12.
   4. 128 + 50 + 25 = £203. Check: 215 − 203 = 12.

10. Answer to Question 10

    1. Add the first two matches in columns: 324 + 289. Ones: 4 + 9 = 13, write 3 carry 1. Tens: 2 + 8 + 1 = 11, write 1 carry 1. Hundreds: 3 + 2 + 1 = 6. Total 613 fans.
    2. Add the third match: 613 + 356. Ones 3 + 6 = 9, tens 1 + 5 = 6, hundreds 6 + 3 = 9. Total 969 fans.
    3. Find the difference: 356 − 289. Count on from 289: 11 to reach 300, then 56 to reach 356. 11 + 56 = 67 more fans.
    4. Count on from 324 to 1000: 76 to reach 400, then 600 to reach 1000. 76 + 600 = 676 empty seats.

11. Answer to Question 11

    1. Add 465 + 238 in columns. Ones: 5 + 8 = 13, write 3 carry 1. Tens: 6 + 3 + 1 = 10, write 0 carry 1. Hundreds: 4 + 2 + 1 = 7. The library has 703 books.
    2. Take away 56: 703 − 56. 703 − 3 = 700, 700 − 53 = 647. 647 books remain.
    3. 29 books come back, so add: 647 + 30 = 677, then take 1 away: 676 books on the shelves.
    4. Only the non-fiction books change: 238 + 100 = 338. Adding 100 makes only the hundreds digit go up by 1.

12. Answer to Question 12

    1. Add the first two parts: 285 + 340. 285 + 300 = 585, then 585 + 40 = 625 m.
    2. Add the third part: 625 + 175. 625 + 100 = 725, then 725 + 75 = 800 m.
    3. The signpost says 1000 m. Count on from 800 to 1000: 200 m further.
    4. Find the difference between 340 and 175: count on 25 to reach 200, then 140 to reach 340. 25 + 140 = 165 m longer.

13. Answer to Question 13

    1. 235 − 187 = 48. Anya has 48 more.
    2. 187 + 235 = 422.
    3. 422 − 90 = 332.
    4. Tom: 187 + 24 = 211. Anya: 235 − 24 = 211. They now have the same number!

14. Answer to Question 14

    1. 124 + 207 = 331.
    2. 331 + 96 = 427.
    3. 600 − 427 = 173.
    4. 100 + 200 + 100 = 400. 427 is close to 400.

15. Answer to Question 15

    1. £236 + £187 = £423.
    2. 423 + 215 = £638. Plant stall £215.
    3. 900 − 638 = £262.
    4. 638 + 150 = 788, which is less than 900. No. They still need £112.

16. Answer to Question 16

    1. 248 + 176 + 120 = 544.
    2. 544 − 315 = 229.
    3. 500 − 315 = 185.
    4. 248 + 120 = 368. 248 + 176 = 424. 368 is less than 424, so Zoe is right.

17. Answer to Question 17

    1. Ones: 6 + 8 = 14, so he must carry 1 ten, and tens 4 + 7 + 1 = 12, so he must carry 1 hundred. He forgot to carry. Correct: 346 + 278 = 624. His answer is wrong.
    2. 703 − 456 = 247. He took the smaller digit from the larger. The correct answer is 247.
    3. Ones 9 + 1 = 10, tens 1 + 8 + 1 = 10, hundreds 2 + 4 + 1 = 7. Right: 700.
    4. 500 − 237: 237 + 263 = 500. Right.

18. Answer to Question 18

    1. 28 + 31 + 29 = 88.
    2. 120 − 88 = 32.
    3. 32 − 11 = 21.
    4. 88 − 29 = 59. Estimate: 90 − 30 = 60, close to 59.

19. Answer to Question 19

    1. 126 + 258 = 384 km.
    2. 384 − 297 = 87 km.
    3. 384 + 384 = 768 km.
    4. 800 − 768 = 32 km.

20. Answer to Question 20

    1. Put the biggest digits in the hundreds places: 6 and 5. Then the next biggest in the tens: 4 and 3. Then the ones: 2 and 1. For example 631 and 542. 631 and 542.
    2. 631 + 542 = 1173.
    3. Put the smallest digits in the hundreds: 1 and 2, then 3 and 4 in the tens, then 5 and 6 in the ones: 135 + 246 = 381.