I am a sum that results in twenty-one. If you subtract me from thirty, you get my other half. What am I?
Category: Math · Difficulty: hard
Hint: Think about the properties of numbers.
Answer
Eleven
Explanation
Eleven plus ten equals twenty-one, and thirty minus eleven equals nineteen, which is another way to express this relationship.
This is a hard math riddle — a tricky one that takes a little thought. The answer is Eleven.
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