题干

某个体养鱼户为估计池塘养鱼的数量,从中打捞了100条鱼,分别作了记号,又放回鱼塘,等鱼混合均匀后,又捕捞了200条,其中有5条鱼有记号,请你估计该池塘共有多少条鱼?
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答案(点此获取答案解析)

解:设鱼塘中的鱼有x条,则 200
5
=100
x
解得x=4000.
则估计池塘共有4000条鱼

同类题3

阅读理解

    Many people traveled to Las Vegas, Nevada last week for the 50th Consumer Electronics Show, or CES. The show is said to have the largest collection of new electronic devices in the world.

    The show had many examples of “smart home” devices. “Smart home” technology is designed to make life easier for people by letting computers control many things inside our homes. One such device actually begins working outside the home, when someone arrives and rings the doorbell.

    “When someone comes to your front door and rings the doorbell, the light can turn on immediately. I get a notification when I'm halfway around the world that someone came, and I can start talking to the person who's at my front door, and I can say, 'Oh, here let me let you in,' I can unlock the door for them very easily.” Said Vivint, a smart home service provider.

    One electronics maker launched a device that lets people see and interact with their animals when they are away. The device, from Petcube, lets you remotely watch and talk to your pet through a personal device, according to a company official. It can even give the pet a treat—if you approve and order it.

    For heating or cooling, there is a smart thermostat. This device can also send you a message if a big storm causes leaks of flooding. “We're trying to catch it with just a few drips before it becomes a real big problem,” said Mike Sale of iDevices.

    A concern for many homeowners is the possibility that someone else might find a way to attack these smart home devices. An official from Vivint said his company is sure that only owners of the home can gain use of information on the devices. Warren Katz from iDevices said his company employs engineers from the defense industry to help prevent hacking.

同类题5

阅读下列文言文,完成后面小题。

刑部尚书富察公神道碑

袁枚

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(选自(《小仓山房文集》,有删节)