What to notice
Every answer in the 8s is even, and the ones digits run 8, 6, 4, 2, 0 and then repeat: 8, 16, 24, 32, 40, then 48, 56, 64, 72, 80. It is a quick check: 8 × 7 has to end in 6, because it is the seventh answer.
Each answer is double the matching answer in the 4s: 4 × 7 = 28, so 8 × 7 = 56. If the 4s are solid, putting the two lists side by side is a good way in.
8 × 8 = 64 is a square, and a chessboard is an 8 by 8 grid of 64 squares. If you have a chess or checkers board at home, counting its rows of 8 is a nice way to see the fact.
Because 8 is 10 − 2, there is a second route for a child who knows the 10s: 8 × 7 is 10 × 7 = 70 take away 2 × 7 = 14, and 70 − 14 = 56. It is handy for 8 × 9 and 8 × 12 in particular, where the doubling gets into bigger numbers.
How to practise at home
- Say the triple double aloud a few times a day: “8 × 3: 6, 12, 24.” Once it is quick, ask for the answer only.
- Use spider legs or octopus arms, 8 each. “Three spiders, how many legs?” is a good silly question for a car ride.
- Pair each fact with its 4s partner: ask 4 × 6 and then 8 × 6, so your child hears the doubling between them.
- The drill on this page shows which 8s are slow. Pick those two or three and practise only them for a few days.
Slips to watch for
- Mixing up 8 × 7 = 56 and 8 × 6 = 48. The endings help: 8 × 6 ends in 8, and 8 × 7 ends in 6.
- Doubling only twice and answering 24 for 8 × 6, which is 4 × 6. Count the doublings on fingers: one, two, three.
- Losing track in 8 × 12. Split it: 8 × 10 = 80 and 8 × 2 = 16, then 80 + 16 = 96.