Number bases

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Each question gives you a number in one base and names the base to write it in. Type that number in the answer box and check it.

A base is how many digits a number system has. Decimal has ten. Binary has two, octal has eight, and hex has sixteen. Hex writes ten to fifteen as A to F. In every base, each place is worth the base times the place to its right, so the binary places are 1, 2, 4, 8 and so on.

Level 1 is decimal and binary, both ways, up to 63. Level 2 is decimal and hex, both ways, up to 255. Level 3 is binary and hex, both ways, up to 255, where four binary digits make one hex digit. Level 4 is any pair of decimal, binary, octal and hex, up to 4095.

Hex is accepted in upper or lower case. A leading 0b, 0o or 0x is ignored, so 0x1A, 1a and 01a all count as the same answer. The one exception is 0b in a hex answer, because b is a hex digit there. Spaces and extra zeros at the front are ignored too.

An untimed round shows the working after each answer, right or wrong. A 2-minute sprint gives you two minutes for all twelve questions. It moves straight to the next question and keeps the working for the questions you miss.

Your score is how many of the twelve you answered correctly. It is practice at reading numbers, not a measure of ability. Finish the round to save it in this browser. A sprint whose clock runs out is saved, as long as you answered one question. Questions you did not reach count as wrong. Ending a round early saves nothing.

Type the answer. Enter checks it. In an untimed round Enter again moves to the next question. Escape ends the round. End ends it too, except while the caret is in the answer box.