The two walked towards the school... Gong Yaqiao was walking on the steps... Hey... Hong shouted!

Gong Yaqiao: It’s you? What are you doing in school?

Hong: Reading!

Gong Yaqiao: No, right??

Han: Yes... Can you take us to the principal's office? We need to register!

Gong Yaqiao said, "Yes... Come with me! Han and Hong were taken to the principal's office... and entered the door. They saw various awards placed on the wall...

The principal is a bald man... very old... probably in his 60s...

Principal: Gong Yaqiao, please go out to class first...

Principal: Are you here to sign up??

Han: I'm here to apply for a teacher... He is my friend... I'm here to sign up for a student!

Principal: It’s okay to sign up to be a student...but you are so young and only 22 years old... Can you be a teacher?

Han: Age cannot judge a person’s ability. You can test me!

Principal: Then I will test you... I ask the study group where Xiao Ming is located decided to measure the density of one-yuan coins. Xiao Ming said: I found a way to use ten exactly the same one-yuan coins, stack them up, measure the total thickness, then place them side by side on the same line, measure their total length, then place them on a balance to measure their total mass, calculate the thickness and radius of each coin, thus calculate the volume of each coin, then calculate the mass of each coin, and then calculate the density of the coin.

Solve the following problems

1 If the thickness of each coin is d                                                                                                                          

2 Some students have some inadequate considerations about Xiao Ming's method, which has caused errors. They must use completely different methods to make the results more accurate.

1 If you do not use a measuring cylinder and a scale, you can choose other equipment. Please design two completely different methods.

2What do you think is the inadequate consideration of Xiao Ming?

Han thought for a while and looked at Hong next to him. Hong had already known what the answer was... Hong winked. He called Han to speak to the mouth, and he said the answer... Han understood what Hong meant... and said to the mouth...

1 If the thickness of each coin is d                                                                                                                          

1 If you do not use a measuring cylinder and a scale, you can choose other equipment.

1. Use the buoyancy scale to find the water spring scale with a thin wire beaker

A few coins were tied to thin threads to measure his gravity in the air

Hang on a spring scale and immerse it in water to measure the number of spring scales

Hong finished speaking... looking at the principal... he probably didn't know. After all, the principal is old... and Han and Hong cooperate well... he shouldn't find anything!

The principal looked at Han... and looked at Hong... Well... you passed the test... I wonder which subject you want to teach???

Han thought about it... let's teach some easy things... and answered...art!

Principal: It's okay... we are missing an art teacher... the salary is 120 yuan per month. It doesn't include food and accommodation...

Hong: How much does it cost to register for me?

The principal looked at Hong. Bai Hair... and thought he wouldn't be a student of any kind. Then he said... You dye your hair black...

Hong: I am sick. I am in poor health. So my hair is white. It is useless to dye it!

Principal: That's right? Then you should pay attention to your class. If you feel uncomfortable, our school has special medical measures!

Hong: Yes...I know!

Principal: The registration fee is 50 yuan per semester... Another 10 yuan book fee and 20 yuan clothing fee!

Hong gave the principal 80 yuan... Can I go to school now???

Principal: You two come here to register...

Registered... I walked out of the door... Han exhaled... I was fine if I did not take the exam... I just took physics...

Hong: Fortunately, I am good at it... OK... I won't say much, where are you arranged?

Han: Class 3 on the third floor! Where are you?

Hong: Class 7, 2nd floor... Let's go...you go up and teach first...I'll take a break...!

Han ran to the third floor... Several girls were discussing...

Leng Xier: I heard that there were two handsome guys in the school... It seems that one of them teaches us art...
Chapter completed!