C.1004. A princess was kidnapped and the kidnappers told the king that they will ask for a ransom between 1 golden coin and 31 golden coins. Therefore, the king put a total of 31 golden coins in a few bags, so when he meets the kidnappers, he could pay any amount between 1 and 31 coins they ask for without having have to open any of the bags. At least how many bags did the king need?
C.1005. Write down the natural numbers from 1 to 100,000 and count how many digits you had to write down. Then write down the natural numbers from 1 to 1,000,000 and count how many zeros you had to write this time. Prove that these two numbers are the same.
C.1006. You have three cards with one digit written on each. You form all possible 1-, 2-, and 3-digit numbers. The sum of all of these numbers is 5635. What are the digits on the cards?
C.1007. ABC is an equilateral triangle with side 6. Let P be a point with distances x,y,z from the three vertices (where X is less than or equal to Y which is less than or equal to Z). Find the area of the region enclosed by all points such that x+y=z.
C.1008. A fully charged cellular phone can work in a standby position (which means that we do not use it for making phone calls) for 72 hours, or we can talk continually for 3 hours on it, and then we have to recharge it again. This cell phone, after it was fully charged, was in standby position for 27 hours, and the owner conducted a 45-minute conversation, also. How many more minutes could we talk on this phone?
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