16 reviewed tricks · one shared maths engine

Trick & Tell

The surprise is memorable. The reason is the real trick.

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Daily Trick · 2026-09-08

One strategy, three real difficulty levels.

Today everyone learns Compensation Addition. Choose how much calculation and reasoning support you want.

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Current streak: 0 · untimed

Four ways to play

Understand it alone. Recognise it anywhere. Reveal it together.

Daily Trick

One deterministic 3–5 minute challenge with Starter, Developing and Challenge levels.

Learn a Trick

Complete Surprise, Discover, Understand, Practise, Spot and Tell stages.

Trick Detective

Investigate when a strategy fits, fails, or is mathematically valid but inefficient.

Trick Party

Private room-code maths magic for friends, families and classrooms.

The library

16 reviewed strategies

01Bridge to a Friendly TenSplit one addend to reach the next multiple of ten, then add what remains.02Near DoublesUse a known double and make one small adjustment.03Compensation AdditionReplace a near-friendly addend with a friendly number, then compensate for the change.04Same-Change SubtractionShift both numbers equally so the subtrahend becomes friendly.05Multiply by 5Use ×10, then halve the result.06Multiply by 9Use ×10, then subtract one copy of the original number.07Multiply a Two-Digit Number by 11Add the two digits and place the result between them, carrying when the digit sum reaches ten.08Multiply by 15Split ×15 into ×10 and ×5, then combine the two friendly products.09Double and HalveHalve one even factor and double the other without changing the product.10Multiply by 25Use ×100, then divide the result by 4.11Multiply by 50Use ×100, then halve the result.12Multiply by 99Use ×100, then subtract one copy of the original number.13Square a Number Ending in 5Multiply the digits before the final 5 by the next whole number, then finish with 25.14Meet in the MiddleMultiply equally spaced factors using midpoint squared minus distance squared.15Square Near 100Square a number close to 100 by adjusting 10,000 with two smaller terms.16Same Front, Ones Make 10Multiply numbers with matching front digits and final digits that add to ten.

Mastery without pressure

Three separate marks

Use It rewards accurate calculation. Spot It checks whether the method fits. Explain It checks reasoning. Lessons are complete regardless of score, and earned marks are never removed.

Use It: 4 of 5 calculations
Spot It: 3 of 4 conditions
Explain It: 2 of 2 reasons

Trick & Tell FAQ

Is this just a list of shortcuts?

No. Every lesson includes a surprise, exact conditions, guided discovery, a proof, independent practice, applicability reasoning, and an optional performance card.

Is it timed?

Lessons and Trick Detective are untimed. Daily Trick is designed to be short but awards no speed bonus.

Do children need accounts?

No. Nickname-only profiles and mastery stay in local browser storage.

Can a shortcut give the wrong answer?

The shared engine validates exact input conditions and direct arithmetic. Trick Detective explicitly teaches when a method does not fit.

Are there ads during play?

No. Active lessons, Daily Trick, Detective, lobbies, party rounds, and reveals suppress ads.

What does Tell It collect?

Nothing. The card supports an in-person performance and does not record audio, video, or free text.