Stage 6 · Big numbers & speed
Three-digit × one-digit
Hundreds, tens, ones: multiply each, add.
How to do it
Method
Hundreds, tens, ones: multiply each, add
347 × 6 = 1800 + 240 + 42 = 2082
Another way
Column multiplication
7 × 6 = 42, write 2 carry 4; 4 × 6 + 4 = 28, write 8 carry 2; 3 × 6 + 2 = 20 → 2082
In full
Split the three-digit number into hundreds, tens and ones, multiply each by the one-digit number, and add: 347 × 6 → 300 × 6 = 1800, 40 × 6 = 240, 7 × 6 = 42, 1800 + 240 + 42 = 2082. A place holding 0 needs no multiplying: 305 × 4 → 300 × 4 = 1200, 5 × 4 = 20, 1200 + 20 = 1220. With the one-digit number in front it's the same: 6 × 347 has the same product as 347 × 6. Estimate first as a check: 347 is near 350, 350 × 6 = 2100, so the answer should be near 2100. Another way is to multiply in columns from the ones, carrying into the next place: 7 × 6 = 42, write 2 carry 4; 4 × 6 + 4 = 28, write 8 carry 2; 3 × 6 + 2 = 20 → 2082 — the same answer.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
900 × 2
Show the answer and working
Answer: 900 × 2 = 1800
900 × 2: split 900 into 900, 900 × 2 = 1800
Example 2
270 × 2
Show the answer and working
Answer: 270 × 2 = 540
270 × 2: split 270 into 200 + 70, 200 × 2 = 400, 70 × 2 = 140, 400 + 140 = 540
Example 3
975 × 5
Show the answer and working
Answer: 975 × 5 = 4875
975 × 5: split 975 into 900 + 70 + 5, 900 × 5 = 4500, 70 × 5 = 350, 5 × 5 = 25, 4500 + 350 = 4850, 4850 + 25 = 4875
Example 4
6 × 393
Show the answer and working
Answer: 6 × 393 = 2358
6 × 393: the order can swap, so work out 393 × 6. 393 × 6: split 393 into 300 + 90 + 3, 300 × 6 = 1800, 90 × 6 = 540, 3 × 6 = 18, 1800 + 540 = 2340, 2340 + 18 = 2358
Practise three-digit × one-digit in the game →Stage 6 · Big numbers & speed · Free to start, unlimited questions, no download