Exercise 1
What to do
Use the information given to you to derive the answer to a similar problem.
If 9 × 20 = 180 what is 9 × 21 180
If 8 × 30 = 240 what is 8 × 31 248
If 4 × 40 = 160 what is 4 × 42 168
If 5 × 50 = 250 what is 5 × 51 255
If 3 × 60 = 180 what is 3 x 62 186
If 2 × 70 = 140 what is 2 × 73 146
If 4 × 80 = 320 what is 4 × 82 328
8) If 2 × 90 = 180 what is 2 × 94 188
Exercise 2
What to do
Use the information given to you to derive the answer to a similar problem.
1) If 9 × 20 = 180 what is 9 × 19 171
2) If 8 × 30 = 240 what is 8 × 29 232
3) If 7 × 40 = 280 what is 7 × 39 224
4) If 5 × 50 = 250 what is 5 × 49 245
5) If 3 × 60 = 180 what is 3 × 58 174
6) If 2 × 70 = 140 what is 2 × 67 134
7) If 4 × 80 = 320 what is 4 × 78 312
8) If 2 × 90 = 180 what is 2 × 86 1 72
Exercise 3
What to do
Use the information given to you to derive the answer to a similar problem.
If 9 × 20 = 180 what is 9 × 22 198
If 7 × 30 = 210 what is 7 × 32 224
If 5 × 40 = 200 what is 5 × 43 215
If 4 × 50 = 200 what is 4 × 51 204
If 3 × 60 = 180 what is 3 × 61 183
If 6 × 70 = 420 what is 6 × 73 438
If 6 × 80 = 480 what is 6 × 81 186
8) If 8 × 90 = 720 what is 8 × 92 736
Exercise 4
What to do
Use the information given to you to derive the answer to a similar problem.
If 9 × 20 = 180 what is 9 × 18 162
If 7 × 40 = 280 what is 7 × 37 259
If 5 × 40 = 200 what is 5 × 38 190
If 4 × 50 = 200 what is 4 × 47 188
If 3 × 60 = 180 what is 3 × 56 171
If 6 × 70 = 420 what is 6 × 67 402
If 6 × 80 = 480 what is 6 × 78 468
8) If 8 × 90 = 720 what is 8 × 88 704
Exercise 5
What to do
Use the information given to you to derive the answer to a similar problem.
If 4 × 200 = 800 what is 4 × 201 804
If 7 × 300 = 2100 what is 7 × 301 2017
If 8 × 400 = 3200 what is 8 × 402 3216
If 9 × 500 = 4500 what is 9 × 501 4509
If 5 × 600 = 3000 what is 5 × 602 3010
If 3 × 700 = 2100 what is 3 × 704 2112
If 2 × 800 = 1600 what is 2 × 803 1606
8) If 6 × 900 = 5400 what is 6 × 903 5418
Exercise 6
What to do
Use the information given to you to derive the answer to a similar problem.
If 4 × 200 = 800 what is 4 × 199 ?
If 7 × 300 = 2100 what is 7 × 299 ?
If 8 × 400 = 3200 what is 8 × 398 ?
If 9 × 500 = 4500 what is 9 × 498 ?
If 5 × 600 = 3000 what is 5 × 597 ?
If 3 × 700 = 2100 what is 3 × 698 ?
If 2 × 800 = 1600 what is 2 x 797 ?
If 6 × 900 = 5400 what is 6 × 897 ?
Exercise 7
What to do
Use the information given to you to derive the answer to a similar problem.
If 2 × 25 = 50 what is 2 × 24 48
If 4 × 25 = 100 what is 4 × 27 92
If 3 × 15 = 45 what is 3 × 14 42
If 4 × 15 = 60 what is 4 × 17 68
If 6 × 15 = 90 what is 6 × 14 84
If 2 × 25 = 50 what is 2 × 26 52
If 4 × 25 = 100 what is 4 × 24 96
If 3 × 15 = 45 what is 3 × 16 48
If 4 × 15 = 60 what is 4 × 13 52
If 6 × 15 = 90 what is 6 × 17 102
Exercise 8
What to do
Use the strategy add a little/subtract a little to solve these problems.
Julie wanted to find 3 × 28.
She knows that 28 is near 30, so she used 3 × 30 = 90 and subtracted 3 × 2 = 6 to get the answer.
Julie recorded this in her maths book
3 × 28 = 90 – 6 = 84
Using Julie’s method find the answer to the following problems. Record your working like Julie did.
1) 4 × 19 76 (2) 3 × 41 121 (3) 5 × 59 295
4) 7 × 52 364 (5) 4 × 73 292 (6) 3 × 37 111
7) 6 × 102 612 (8) 5 × 301 1502 (9) 4 × 698 2792
10) 3 × 499 1497 (11) 7 × 602 4214 (12) 9 × 3999 35,991