3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 324 · 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. 1.665 + 231 =
2. 2.443 − 167 =
3. 3.616 + 339 =
4. 4.273 + 144 =
5. 5.427 + 539 =
6. 6.665 − 337 =
7. 7.511 − 281 =
8. 8.638 − 457 =
9. 9.687 + 508 =
10. 10.254 + 399 =
11. 11.148 + 577 =
12. 12.340 + 274 =
13. 13.592 + 633 =
14. 14.775 − 251 =
15. 15.962 − 851 =
16. 16.818 − 281 =
17. 17.526 − 354 =
18. 18.952 − 803 =
19. 19.624 + 386 =
20. 20.693 + 219 =
21. 21.898 − 606 =
22. 22.706 + 413 =
23. 23.313 + 205 =
24. 24.452 + 305 =
25. 25.772 + 583 =
26. 26.429 + 629 =
27. 27.638 − 383 =
28. 28.644 − 162 =
29. 29.511 + 523 =
30. 30.687 − 279 =
31. 31.980 − 119 =
32. 32.205 + 291 =
33. 33.681 − 251 =
34. 34.974 − 419 =
35. 35.623 − 388 =
36. 36.448 − 119 =
37. 37.175 + 163 =
38. 38.550 − 309 =
39. 39.624 + 287 =
40. 40.219 + 588 =

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