Start with the gaps
Subtract neighboring terms first. If the gap stays the same, adding a fixed number may explain the pattern. In 4, 7, 10, 13, each step adds 3, so the next number under that rule is 16.
When gaps change, try a ratio
The gaps in 3, 6, 12, 24 are 3, 6, and 12. But each term is twice the one before it. Following that rule gives 48. A pattern that fails an addition check may still follow multiplication.
Look at every other number
Split 2, 9, 4, 12, 6, 15 into alternating positions: 2, 4, 6 and 9, 12, 15. Two simpler patterns may be woven together. Try separating odd and even positions when one rule does not fit.
Explain the rule you chose
A short sequence can fit more than one mathematical rule. This game asks you to choose among the options using its intended rule; it does not claim that only one rule is mathematically possible. Compare your reasoning with the explanation after answering.
Original game guides and worked math examples by BrainOtter. No health or cognitive improvement claims are made.