Let’s solve each problem using Carrie’s method:
Halve one number (to get a single digit) and double the other, then multiply.
We’ll go step by step for each problem.
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1) 14 × 24
Which number can we halve to get a single digit?
→ 14 ÷ 2 = 7 (single digit!) → so halve 14, double 24
→ 24 × 2 = 48
Now calculate:
7 × 48
Break it down:
7 × 40 = 280
7 × 8 = 56
280 + 56 =
336
✔ Check with calculator: 14 × 24 = 336 ✔️
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2) 31 × 14
Can we halve 31? → 31 ÷ 2 = 15.5 → not whole → skip
Can we halve 14? → 14 ÷ 2 = 7 → yes!
So halve 14 → 7, double 31 → 62
Now calculate:
7 × 62
7 × 60 = 420
7 × 2 = 14
420 + 14 =
434
✔ Check: 31 × 14 = 434 ✔️
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3) 43 × 12
Halve 12 → 6 (single digit), double 43 → 86
Calculate:
6 × 86
6 × 80 = 480
6 × 6 = 36
480 + 36 =
516
✔ Check: 43 × 12 = 516 ✔️
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4) 35 × 12
Halve 12 → 6, double 35 → 70
Calculate:
6 × 70 = 420
✔ Check: 35 × 12 = 420 ✔️
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5) 14 × 27
Halve 14 → 7, double 27 → 54
Calculate:
7 × 54
7 × 50 = 350
7 × 4 = 28
350 + 28 =
378
✔ Check: 14 × 27 = 378 ✔️
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6) 16 × 38
Halve 16 → 8, double 38 → 76
Calculate:
8 × 76
8 × 70 = 560
8 × 6 = 48
560 + 48 =
608
✔ Check: 16 × 38 = 608 ✔️
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7) 17 × 18
Halve 18 → 9, double 17 → 34
Calculate:
9 × 34
9 × 30 = 270
9 × 4 = 36
270 + 36 =
306
✔ Check: 17 × 18 = 306 ✔️
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8) 16 × 16
Halve 16 → 8, double 16 → 32
Calculate:
8 × 32
8 × 30 = 240
8 × 2 = 16
240 + 16 =
256
✔ Check: 16 × 16 = 256 ✔️
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9) 18 × 49
Halve 18 → 9, double 49 → 98
Calculate:
9 × 98
9 × 100 = 900 → but 98 is 2 less → so subtract 9×2=18
900 - 18 =
882
Or break it down:
9 × 90 = 810
9 × 8 = 72
810 + 72 =
882
✔ Check: 18 × 49 = 882 ✔️
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Final Answer:
1) 336
2) 434
3) 516
4) 420
5) 378
6) 608
7) 306
8) 256
9) 882
Parent Tip: Review the logic above to help your child master the concept of multiply multi digit number worksheet.
