Stage 6 · Big numbers & speed
Two-digit × one-digit
Split into tens and ones; multiply each, add.
How to do it
Method
Split into tens and ones; multiply each, add
34 × 7 = 30 × 7 + 4 × 7 = 210 + 28 = 238
Another way
Column multiplication
Ones 4 × 7 = 28, write 8, carry 2; tens 3 × 7 + 2 = 23 → 238
In full
Split into tens and ones, multiply each, add. 34 × 7 → 30×7=210, 4×7=28, total 238. That's the distributive property — the skeleton under every long multiplication. Column multiplication does the same, starting from the ones.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
13 × 7
Show the answer and working
Answer: 13 × 7 = 91
13 × 7: split 13 into 10 and 3, 10 × 7 = 70, 3 × 7 = 21, 70 + 21 = 91
Example 2
13 × 9
Show the answer and working
Answer: 13 × 9 = 117
13 × 9: split 13 into 10 and 3, 10 × 9 = 90, 3 × 9 = 27, 90 + 27 = 117
Example 3
21 × 9
Show the answer and working
Answer: 21 × 9 = 189
21 × 9: split 21 into 20 and 1, 20 × 9 = 180, 1 × 9 = 9, 180 + 9 = 189
Example 4
28 × 9
Show the answer and working
Answer: 28 × 9 = 252
28 × 9: split 28 into 20 and 8, 20 × 9 = 180, 8 × 9 = 72, 180 + 72 = 252
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