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Practice centre
Pick a technique, get 10 questions generated locally. Nothing is uploaded while you drill. Goal: below three seconds per question.
Time 0:00
Mode: Multiply by 11 | questions: 10
Choose a mode and a level, then press "Start a set". Questions appear below and are marked together at the end.
How to drill (from the source book's training advice)
- Slow before fast: for the first 20 questions say the steps out loud. Speed comes after the sequence is automatic.
- Never guess: verify each answer with the DS digital root — two seconds, every time.
- Ten minutes daily: frequency beats duration. Three days off costs you about 20% of your speed.
- Review misses: a wrong answer maps to one step of one technique. Go back and read only that step.
Modes and the lessons behind them
| Mode | Lesson | Core move |
|---|---|---|
| Multiply by 11 | Multiplying by 11 | neighbour sums, carry in place |
| Square ending in 5 / any two digits | Fast squaring | first×(first+1) then 25; round and compensate |
| Multi-digit × one digit | LR multiplication | multiply from the left, merge as you go |
| LR add / subtract | LR addition & subtraction | left to right, complement compensation |
| Bridge method | Bridge method | first × first, cross, last × last |
| UT method | UT method | units lane and tens lane, then merge |