3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 302 · 40 questions

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

1. 1.518 + 274 =
2. 2.670 − 261 =
3. 3.603 + 219 =
4. 4.616 − 178 =
5. 5.635 − 515 =
6. 6.210 + 331 =
7. 7.310 + 361 =
8. 8.579 − 139 =
9. 9.477 − 184 =
10. 10.775 + 628 =
11. 11.211 + 435 =
12. 12.583 + 645 =
13. 13.693 − 555 =
14. 14.662 + 155 =
15. 15.457 + 438 =
16. 16.629 + 329 =
17. 17.747 − 335 =
18. 18.972 − 223 =
19. 19.513 + 305 =
20. 20.181 + 183 =
21. 21.580 − 205 =
22. 22.189 + 339 =
23. 23.757 − 551 =
24. 24.568 + 357 =
25. 25.160 + 239 =
26. 26.503 − 154 =
27. 27.714 + 237 =
28. 28.714 + 256 =
29. 29.463 − 283 =
30. 30.505 − 371 =
31. 31.394 + 128 =
32. 32.771 − 284 =
33. 33.572 − 344 =
34. 34.460 + 537 =
35. 35.673 − 419 =
36. 36.571 − 141 =
37. 37.966 − 695 =
38. 38.415 − 238 =
39. 39.477 − 121 =
40. 40.425 + 232 =

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