A stack of cards is numbered sequentially from 1 to 50. First, you remove all odd-numbered cards. Then, from the remaining cards, you remove every card that is a multiple of 4. How many cards remain in the stack?
13 cards
Removing odd cards leaves 25 even cards (2, 4, 6, ..., 50). The multiples of 4 up to 50 are 4, 8, 12, ..., 48, which accounts for 12 cards. Subtracting these 12 cards from the 25 even cards leaves 13 cards.
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.
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