Missing Number

Missing Number is a number-pattern quiz against the clock. Six numbers are shown in a row with one of them hidden. Work out the rule that links them and pick the number that belongs in the gap from four choices.

The first sequences simply count up in equal steps. As your score grows, the game adds sequences that count down, sequences that double or triple each time, sequences where the gap between numbers grows by one at every step, and rows of square numbers. The hidden number can then be anywhere in the row, including the very start. You have 75 seconds, and a wrong answer takes five seconds off the clock, so a moment of thought is worth more than a guess.

Choose the number that completes each sequence. You have 75 seconds; each wrong answer costs five seconds.