Quantitative Reasoning · Hard · 1 of 16
Number Series puzzle #1 (hard)
Which number comes next? Tap an option to check your answer, or show the answer for the step-by-step solution. Rule in play: double plus a constant.
Plate 01 / 16 · Hard
Which number comes next?
7, 15, 31, 63, 127, ?
Tap the option you think is right, or show the answer.
Show the answer
The next number is 255 (option 5).
How to solve it
- Doubling gets close: 7 × 2 = 14, and the next number is 15.
- Each number is double the one before, plus 1.
- So the next number is 127 × 2 + 1 = 255.
About this puzzle
Hard series add the two previous numbers, double and add a constant, double the gaps, or alternate two operations. It was generated by the same engine that builds the IQ Octopus test, from a fixed seed, so it stays the same every time you visit. In the real test, items like this are generated fresh for every attempt.
New to this format? Read how to solve them, or time yourself on 10 in a row with the practice test.
Related
- No. 01Hard number series16 hard puzzles with answers and worked solutions.
- No. 02Number Series puzzles50 puzzles, easy to hard. Which number comes next?
- No. 03Number sequence testTen number series, 30 seconds each. Find the rule.
- No. 04Number seriesThe rules behind number series, and a method that finds them.
25 puzzles · about 12 min
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