3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 679 · 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. 1.139 + 682 =
2. 2.577 + 144 =
3. 3.526 + 164 =
4. 4.618 + 607 =
5. 5.499 − 151 =
6. 6.422 + 542 =
7. 7.624 − 445 =
8. 8.638 + 475 =
9. 9.886 − 311 =
10. 10.607 − 466 =
11. 11.730 + 197 =
12. 12.535 + 556 =
13. 13.144 + 168 =
14. 14.399 + 469 =
15. 15.192 + 425 =
16. 16.862 − 349 =
17. 17.408 + 179 =
18. 18.639 + 175 =
19. 19.664 − 453 =
20. 20.892 − 177 =
21. 21.424 + 321 =
22. 22.373 + 152 =
23. 23.756 + 675 =
24. 24.320 + 667 =
25. 25.409 + 277 =
26. 26.189 + 118 =
27. 27.434 − 138 =
28. 28.555 − 388 =
29. 29.192 + 245 =
30. 30.585 − 422 =
31. 31.566 − 184 =
32. 32.426 − 221 =
33. 33.825 − 345 =
34. 34.660 − 144 =
35. 35.690 − 291 =
36. 36.300 + 402 =
37. 37.531 − 274 =
38. 38.877 − 122 =
39. 39.297 + 534 =
40. 40.433 + 576 =

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