Math puzzle: calculate the probability of coins facing up.
Calculate the probability of coins facing up.
There is an ordinary coin, and Xiao Wang * * * threw it seven times, and every time it was face up. Now Xiao Wang wants to throw it away again. Do you know the probability of head up?
Answer: There is no doubt that it is half. No matter who throws it, no matter how many times, this probability will not change. Never let inertia lead you into a trap.
Math puzzle: How many nights can the remaining candle heads be used without power?
How many nights can the remaining candle heads be used without power?
A long time ago, Xiao Wang's family often had power cuts. Every time he stops, he uses 1 candle, and every five candle heads can be made into 1 candle. Once, there were only 40 candle heads left in his house. How many nights can these candle heads be used to make candles?
Answer: It can be used for 9 nights. Because 40 candle heads can be made into 8, and they can be made into 1 after use.
Math puzzle: Can you work out the weight of the heaviest wax gourd?
Can you calculate the weight of the heaviest wax gourd?
The weight of the seven east melons (in whole kilograms) increases in turn. The average weight is 7 kilograms. What's the heaviest weight of Donggua?
Answer: 7 is an odd number (calculated in whole kilograms). Now the average weight is 7 kg, and the middle east melon weighs 7 kg, so adding 3 kg or 6 kg is the heaviest east melon. The heaviest pumpkin is 7+3 = 10 kg or 7+6 = 13 kg. The weight of seven pumpkins is: 4, 5, 6, 7, 8, 9, 10. Or: 1, 3,5,7,9,0.11.13.
Math puzzle: Use two different hourglasses to calculate 15 minutes.
Use two different hourglasses to calculate 15 minutes.
Xiao Wang needs to cook a pot of soup for 15 minutes, but there are only two hourglasses beside him, one for 1 1 minute and the other for 7 minutes. How can he work out 15 minutes with these two hourglasses?
Answer: Put two hourglasses here. When the sand in the hourglass leaked out in 7 minutes, he turned it upside down again; At this time, 1 1 min, there are 4 minutes left in the hourglass. When the sand inside leaks out, there is only 4 minutes of sand at the bottom of the 7-minute hourglass. Turn the hourglass upside down for another 7 minutes, so that when the sand leaks out again, the time is exactly 15 minutes.
Math puzzles: put symbols in the correct position of mathematical expressions.
Put the symbol in the correct position of the mathematical expression
The question below is incorrect. However, if you add two minus signs (-) and a plus sign (+) to some numbers on the left side of the equation, you can get a correct mathematical expression and make the result equal to 100. Can you put this symbol in the right place? .
1 2 3 4 5 6 7 8 9 = 100
Add two minus signs (-)
Add a plus sign (+)
Answer: 123-45-67+89= 100.
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