A detective finds a note with five numbers written in sequence: 2, 3, 5, 9, 17. The detective realizes a sixth number was torn off at the end. Following the exact mathematical pattern, what is the missing sixth number?
33
The differences between consecutive numbers double each time: +1, +2, +4, +8. Adding 16 (double of 8) to 17 gives 33. Alternatively, each number is generated by multiplying the previous number by 2 and subtracting 1.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Easy. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
Three runners—Leo, Max, and Sam—each wear a shirt of a different color: Red, Blue, or Green. Max is not wearing the Red shirt. The runner in the Blue shirt finished ahead of Sam. Leo is wearing the Green shirt. What color shirt is Max wearing?
Three boxes are labeled 'Apples', 'Oranges', and 'Apples and Oranges'. Every single label is guaranteed to be incorrect. You are allowed to draw only one fruit from one box to figure out the correct labeling of all boxes. Which box should you pick from?
Two fathers and two sons went on a fishing trip. They caught exactly three fish, and each person caught one fish. How is this possible?
A farmer has a wolf, a goat, and a cabbage to cross a river in a small boat that can only hold the farmer and one item at a time. If left unattended, the wolf eats the goat, and the goat eats the cabbage. How many one-way boat trips does it take to cross safely?
A silent archive holds three identical identical boxes labeled 'Letters', 'Numbers', and 'Symbols'. Every single label is currently placed on the wrong box. You are allowed to blindly draw only one item from a single box to deduce all correct labels. Which box do you choose?
Three people stand in a line facing forward: Person 3 sees Persons 2 and 1; Person 2 sees Person 1; Person 1 sees no one. They are shown 3 red hats and 2 blue hats. Everyone is fitted with a hat. Person 3 says, 'I do not know my hat color.' Hearing this, Person 2 says, 'I do not know my hat color either.' What color hat is Person 1 wearing?