Times tables 8 and 9 · Code with Martin

The last two rows — and you are done

Eight and nine are the last rows you are missing. And both have lovely tricks.

Nine is ten minus one pile. 9 × 6? Work out 10 × 6 = 60 and take away one six: 54. You know ten perfectly, so nine is one extra step.

Eight is triple doubling. 8 × 6? Double: 12. Double: 24. Double: 48. Eight piles = twice four = twice twice two.

Nine has two extra magic tricks. First: the digits of the result always add up to 9 (54: 5 + 4 = 9). Second: a finger trick, which I will show you below.

Once you manage today, you know the whole small times tables. All one hundred facts. The rest of the level builds on them — division, written methods, word problems. That is why we spend so long on the times tables: they are the base everything else stands on.

Sofie saw a finger trick at her older sister’s and did not believe it. She put both hands on the table, fingers spread. “How much is 9 × 4?” her sister asked. “Bend the fourth finger from the left.” Sofie bent it. Left of the bent finger 3 fingers stayed, on the right 6. Sister said: “Thirty-six.” Sofie checked through ten: 10 × 4 = 40, minus 4 is 36. It fits! The whole evening she then tried the trick on every nine — and it worked every time.

💡

Finger trick for nine: put your hands on the table and bend the finger with the order of the second number. Fingers left of the bent one = tens, fingers right = ones. 9 × 4: bend the fourth finger, you see 3 and 6 → 36.

Nine through ten, eight by doubling

Bridge for nine: ten minus a pile.

Example 9 × 7:

Ten piles: 10 × 7 = 70.
Give one pile back: 70 − 7 = 63.

Done: 9 × 7 = 63.

Nine check by adding digits: 63 → 6 + 3 = 9. If the digit sum of a nine-row result is not 9, you have a mistake somewhere. 54 → 9. 72 → 9. 81 → 9. It always works.

Bridge for eight: double three times.

Example 8 × 7:

Double: 7 + 7 = 14.
Double: 14 + 14 = 28.
Double: 28 + 28 = 56.

Done: 8 × 7 = 56. (It matches the helper 5, 6, 7, 8 from the last lesson!)

And the last facts of the whole times tables: 8 × 8 = 64 and 9 × 9 = 81. Learn those by heart — they are the corners of the times-table grid and teachers love asking them.

That gives you all ten rows. From now on we do not practise rows one by one, but everything mixed together — exactly how life asks it.

Nine through ten

Example: 9 × 6.

Step 1: ten piles: 10 × 6 = 60.

Step 2: I give one six back: 60 − 6 = 54.

Check: digit sum 5 + 4 = 9. It fits, it is the nine row.

One more: 9 × 8. Ten eights is 80, minus 8 is 72. Check: 7 + 2 = 9. It fits.

Eight by doubling

Example: 8 × 6.

Step 1: double six: 6 + 6 = 12.

Step 2: double: 12 + 12 = 24.

Step 3: double: 24 + 24 = 48.

Why three doublings? 2 piles, then 4 piles, then 8 piles. Each doubling doubles the number of piles: 2 → 4 → 8.

The finger trick step by step

Example: 9 × 7.

Step 1: put both hands on the table, ten fingers spread.

Step 2: bend the seventh finger from the left (count from the left little finger).

Step 3: read the hands: left of the bent finger there are 6 fingers, on the right 3 fingers.

Step 4: the result is 63 — six tens and three ones.

Check through ten: 70 − 7 = 63. Fingers and the bridge give the same.

⚠️

With nine, watch the taking away: 9 × 6 is 60 − 6, not 60 − 9. You take away one pile, and the pile has 6 pieces. Take away the number you times ten by.

Practice: now you do it 🎲

Now try it for real. You will see all the questions at once, like on paper. Start with ten. When it goes well, add more.

Eights and nines. Nine through ten, eight by doubling.

Practise the questions

On paper

Today you will make your own times-table grid. It takes a moment and lasts for years.

Draw a 10 × 10 grid. In the top row write 1 to 10, in the left column too. In each cell belongs the product of the row and the column.
Fill first the rows you know best (1, 2, 5, 10), then the rest through the bridges. Do not rush.
Highlight the diagonal in colour: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100. Those are squares — a number times itself.
Circle the facts you had to think about the longest. Those are your cards for tomorrow.

Now you 💪

You can do 9 × 7 through ten (70 − 7) and with the finger trick, and both give 63.
You can do 8 × 6 by triple doubling: 12, 24, 48.
You know 8 × 8 and 9 × 9 by heart.

✅

Done when: You know all ten times-table rows, you have a grid filled by your own hand, and you know which facts still need practice.

What to take from this lesson

Nine = ten minus a pile: 9 × 7 = 70 − 7 = 63.
Nine check: the digits of the result always add up to 9.
Eight = double three times: 7 → 14 → 28 → 56.
The finger trick works for the whole nine row.
You have the whole times tables. Now mix them a little every day, so they settle.