Learn a Trick
Choose a complete lesson
Learn one strategy from surprise through proof and practice. Lessons are untimed and award separate Use It, Spot It and Explain It marks.
Who is practising?
Choose a local nickname to keep progress separate. No account is needed.
Use a nickname, not a real student name.
friendly numbers
Bridge to a Friendly TenSplit one addend to reach the next multiple of ten, then add what remains.0/3 marksNear DoublesUse a known double and make one small adjustment.0/3 marksCompensation AdditionReplace a near-friendly addend with a friendly number, then compensate for the change.0/3 marksSame-Change SubtractionShift both numbers equally so the subtrahend becomes friendly.0/3 marks
multiplication magic
Multiply by 5Use ×10, then halve the result.0/3 marksMultiply by 9Use ×10, then subtract one copy of the original number.0/3 marksMultiply a Two-Digit Number by 11Add the two digits and place the result between them, carrying when the digit sum reaches ten.0/3 marksMultiply by 15Split ×15 into ×10 and ×5, then combine the two friendly products.0/3 marksDouble and HalveHalve one even factor and double the other without changing the product.0/3 marksMultiply by 25Use ×100, then divide the result by 4.0/3 marksMultiply by 50Use ×100, then halve the result.0/3 marksMultiply by 99Use ×100, then subtract one copy of the original number.0/3 marks
pattern power
Square a Number Ending in 5Multiply the digits before the final 5 by the next whole number, then finish with 25.0/3 marksMeet in the MiddleMultiply equally spaced factors using midpoint squared minus distance squared.0/3 marksSquare Near 100Square a number close to 100 by adjusting 10,000 with two smaller terms.0/3 marksSame Front, Ones Make 10Multiply numbers with matching front digits and final digits that add to ten.0/3 marks