Adding 9, 19 and 99 Mental Maths Worksheet
How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?
NameDateTime takenScore ___ / 40
- 1.72 − 9 =
- 2.599 + 99 =
- 3.35 + 9 =
- 4.45 + 19 =
- 5.640 − 99 =
- 6.48 + 9 =
- 7.20 + 9 =
- 8.50 + 29 =
- 9.15 + 29 =
- 10.31 − 9 =
- 11.37 − 9 =
- 12.470 − 99 =
- 13.636 + 99 =
- 14.43 − 29 =
- 15.23 − 9 =
- 16.32 + 19 =
- 17.49 − 19 =
- 18.25 + 29 =
- 19.69 − 29 =
- 20.64 − 29 =
- 21.52 − 29 =
- 22.68 + 19 =
- 23.77 + 9 =
- 24.63 + 19 =
- 25.62 + 29 =
- 26.88 − 19 =
- 27.251 + 99 =
- 28.64 − 9 =
- 29.238 + 99 =
- 30.89 − 29 =
- 31.34 + 19 =
- 32.55 − 29 =
- 33.71 + 19 =
- 34.32 + 9 =
- 35.49 − 9 =
- 36.56 − 9 =
- 37.51 − 19 =
- 38.42 − 9 =
- 39.24 − 9 =
- 40.300 + 99 =
Answer key
- 63
- 698
- 44
- 64
- 541
- 57
- 29
- 79
- 44
- 22
- 28
- 371
- 735
- 14
- 14
- 51
- 30
- 54
- 40
- 35
- 23
- 87
- 86
- 82
- 91
- 69
- 350
- 55
- 337
- 60
- 53
- 26
- 90
- 41
- 40
- 47
- 32
- 33
- 15
- 399
Free mental maths lessons, practice and worksheets at talentjr.in/mental-maths