Symbols of the chemical elements
ChemistryMiddle school
From the name of a common chemical element to its symbol, and from the symbol to the name.
Click a card to see its answer. Series no. 446927 — this page’s address gives these exact cards again.
Other series
MathematicsMiddle school
Arithmetic with signed numbers
Adding, subtracting and multiplying signed numbers, where the signs trip up the reflexes.
Computer scienceHigh school
Binary and hexadecimal conversions
Converting a byte between base 2, base 10 and base 16, the way the machine does.
MathematicsMiddle school
Decimal form of simple fractions
Turning a simple fraction into its decimal form, in your head, without doing the division.
MathematicsMiddle school
Linear equations
Solving an equation of the form ax + b = c in your head, with a whole-number solution.
MathematicsMiddle school
Percentages of a number
Taking a simple percentage of a number, and recognising an increase or a decrease.
PhysicsHigh school
Physics and chemistry formulas
The formulas from the syllabus, to be recalled as they stand before knowing how to use them.