Flash questions
Short drills on core skills, drawn at random each time you open one. A wall of cards to project, print or run as a timed slideshow — answers stay hidden until you ask for them.
Times tables
The 2 to 12 times tables, both ways round: the product asked for, or the missing factor.
Decimal form of simple fractions
Turning a simple fraction into its decimal form, in your head, without doing the division.
Percentages of a number
Taking a simple percentage of a number, and recognising an increase or a decrease.
Arithmetic with signed numbers
Adding, subtracting and multiplying signed numbers, where the signs trip up the reflexes.
Squares and square roots
Squares up to 20 and exact square roots, to be recognised without hesitation.
Sums of fractions
Adding or subtracting two fractions and giving the result in its lowest terms.
Linear equations
Solving an equation of the form ax + b = c in your head, with a whole-number solution.
Unit conversions
Lengths, masses, capacities and durations: changing units without a conversion table.
Powers of ten and scientific notation
Moving between scientific notation and decimal form, and back, without a calculator.
Special products
Expanding (a + b)², (a − b)² and (a + b)(a − b) without going back through distributivity.
Special values on the unit circle
The cosines and sines of the special angles, from 0 to π, given without thinking.
Standard derivatives
Recalling the derivative of the reference functions and of powers of x, from memory.
SI units
Matching each physical quantity to its SI unit and to the symbol that denotes it.
Physics and chemistry formulas
The formulas from the syllabus, to be recalled as they stand before knowing how to use them.
Symbols of the chemical elements
From the name of a common chemical element to its symbol, and from the symbol to the name.
Binary and hexadecimal conversions
Converting a byte between base 2, base 10 and base 16, the way the machine does.
Powers of two
From 2¹ to 2¹⁶: the sizes that turn up everywhere in computing, both ways round.
What are flash questions for?
A flash question is answered in seconds, in your head. Strung into a short series, they keep sharp the basics — times tables, fractions, conversions, formulas — that longer exercises already assume. Every wall is drawn afresh: the same series never comes back identical, unless you keep its address.