There is a strange mushroom in the Land of Oz. Every day it grows twice as big as it used to be the day before. Let’s say it took 100 days for the mushroom to grow as large as it can fill one entire cave. How long would it take for two such mushrooms to grow to fill in the same cave?

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he numbers below follow a certain rule.

The number 88 and 63 together produces 25, and 25 and 9 makes 16. Fill in the blank.

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Professor Dumbledore showed 2 white hats and 3 black hats to his students. Then he picked 3 hats among them and put them on Hermione, Ron and Harry. Since they were in a line, they could only see the hats of the people in front; they could not see the hat of themselves or that of the person behind. Professor Dumbledore asked them to find out the color of their hats they were wearing in an order of Harry, Ron and Hermione.

Harry, the last one in the line, said “I don’t know”. Ron, in the middle, after thinking about it for a while said, “I don’t know either”. Hermione, after listening to the answers of others showed a knowing expression, saying, "Aha! The color of my hat is _____. "

Find out the color of Hermione’s hat and explain how she got her answer.

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Look at the following crypt carefully. What is the answer?

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There is a square-shaped land looking like the one below. A river, the width of which is 2m evenly, flows through it. What is the area of the land excluding the area where the river is?

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A, B, C and D had a ba-duk league. Everyone played once or more with others. The result is as follows:

A: 1 win and 2 defeats

B: 3 wins and 0 defeat

C: 0 win and 4 defeats

How many wins and defeats did D have?

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