Symbols of the chemical elements
Going from the name of a chemical element to its symbol, and from the symbol to the name, over the fifty-five most common elements.
Click a card to see its answer. Series no. 883972 — this page’s address gives these exact cards again.
Other series
Areas and perimeters
Working out the area or the perimeter of the usual shapes — square, rectangle, triangle, disc — without opening the formula sheet.
Arithmetic with signed numbers
Adding, subtracting and multiplying signed numbers, where the signs trip up the reflexes.
Binary and hexadecimal conversions
Converting a byte between base 2, base 10 and base 16, the way the machine does.
Complex numbers
Powers of i, modulus and conjugate: the reflexes that save time on any complex-number calculation.
Decimal form of simple fractions
Going from a simple fraction to its decimal form and back to the fraction, in your head, without long division.
Discriminant and roots
Discriminant, sum and product of the roots of a quadratic, read straight off the coefficients.