Excel in math and science
Master concepts by solving fun, challenging problems.
It's hard to learn from lectures and videos
Learn more effectively through short, interactive explorations.
Used and loved by over 7 million people
Learn from a vibrant community of students and enthusiasts,
including olympiad champions, researchers, and professionals.
Excel in math and science
Master concepts by solving fun, challenging problems.
It's hard to learn from lectures and videos
Learn more effectively through short, interactive explorations.
Used and loved by over 7 million people
Learn from a vibrant community of students and enthusiasts,
including olympiad champions, researchers, and professionals.
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In an office with 4 people, the 1 manager always lies and the 3 engineers always tell the truth. Who is the manager?
Alice: "Bob is an engineer."
Bob: "Alice is an engineer."
Carol: "David is the manager."
David: "Carol is the manager."
Alice: "David is the manager."
David: "Alice is the manager."
by
Christopher Boo
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True or False?
\[\large 1\div\Big(2\div (3 \div (4\div ( \cdots \div (2015\div (2016\div 2017) ) \cdots \Big) > 1\]
by
Naren Bhandari
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\(1\) is an \(\color{red}\text{odd}\) number.
\(1 + 2 \) is an \(\color{red}\text{odd}\) number.
\(1 + 2 + 3\) is an \(\color{blue}\text{even}\) number.
\(1 + 2 + 3+ 4\) is an \(\color{blue}\text{even}\) number.
\(1 + 2 + 3+ 4+5\) is an \(\color{red}\text{odd}\) number.
\(\cdots \cdots\)
True or False?
\(1 + 2 + 3 + \cdots + 999 \) is an \(\color{red}\text{odd}\) number.
by
Pi Han Goh
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A rectangle is divided into nine sub-rectangles, as shown in the figure. Inside some rectangles are their respective perimeters.
What is the perimeter of the large, outer rectangle?
by
Ronald Chén
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Sara is returning home from a birthday party in a van. She has a helium balloon tied to the seat in front of her. If the van driver suddenly steps on the brake pedal very hard, what will happen to Sara and her balloon, relative to the van?
by
Worranat Pakornrat
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