Learning centre
Every lesson has the same shape: the rule, a worked derivation, a live demo that runs locally, and a practice set. Nothing here needs a network connection.
Nine techniques that cover most arithmetic
DS Digital Root Check
Reduce both sides of an equation to a single digit; if they disagree, the answer is definitely wrong.
2 min · verification 2Multiplying by 11
First digit, neighbour sums, last digit — carries resolved in place.
6 min · ×11 3LR Addition & Subtraction
Add and subtract from the left, compensating with complements.
8 min · +/− 4LR Multiplication & Splitting
Split by place value, round up and compensate, or factor into easy pieces.
10 min · × 5Fast Squaring
Numbers ending in 5 use first×(first+1) then 25; anything near a round number uses (n−k)(n+k)+k².
8 min · n² 6The Bridge Method
First × first, cross terms, last × last — one pass for two-digit products.
7 min · 2d×2d 7The Vitruvian Man Method
Slice a large product so that every intermediate result stays inside working memory.
9 min · big × 8The UT Method
Run the units lane and the tens lane separately, then merge.
9 min · 4d×2d 9FP Flagpole Division
Write only the divisor's flag; carry a running remainder and read the quotient off directly.
12 min · ÷Speed tricks that transfer to science papers
Physics
- Dimensional analysis — reject impossible options without computing
- Special values & limits — substitute 0, 1 or ∞
- Graphs & geometry — read the answer off a sketch
- Ratios & common constants — keep numbers as ratios as long as possible
Chemistry
- Conservation method — track the atom that never changes
- Difference method — use the mass change directly
- Average-value method — infer composition from a mean
- Unified mole method — convert everything to moles once
Ten minutes a day beats three hours on Sunday
- Read one rule and say it out loud without looking.
- Do 10 questions in the practice centre, same mode for the whole set.
- Verify every answer with the DS method — two seconds each.
- Log the miss. A wrong answer points at one specific step, not at "maths".