python numpy basics | 基础 python numpy 1

Tonight our class played together numpy basics and math.  We put together a numpy basics notebook:
https://nbviewer.jupyter.org/github/magicmathmandarin/PythonBasics/blob/master/numpy_basics1.ipynb#back-to-top

Programming by trial and error is a great way for kids to learn not only programming but also math. — this should play a bigger and bigger role in children’s day to day learning.  玩编程也帮助学习算术。

Somehow I have a feeling that learning long division in this day and age is wrong.  在这个时代还学长除法那就不对了。

Go ahead and tinker with the code in the notebook. Nothing will break, we promise 🙂

To see a world in a grain of sand | 从沙粒看世界

Professor ShouCheng Zhang “passed away”.  He is forever with us, seeing a world in a grain of sand, holding infinity in hand.

这是所有视频里最喜欢的一个视频。 张教授深入浅出,循循善诱。尽管已经“离世”, 张教授永远和我们在一起从沙粒看世界,把永恒留在刹那时光。

We won’t quote any physics or mathematics from the video, except the title of the lecture, originally from William Blake, and dedicate them to Professor Zhang:

To see a world in a grain of sand
And a heaven in a wild flower,
Hold infinity in the palm of your hand
And eternity in an hour.
一颗沙里看出一个世界
一朵野花里一座天堂
把无限放在你的手掌
永恒在一剎那里收藏

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Chinese style education & empty basketball courts |中国式教育和空荡荡的蓝球场

I was in China this November to conduct surveys on education.  I had a few chances of sitting in some after school education programs and cram school classes, including XDF新东方, and was shocked by the amount of work Chinese kids have to do and was saddened by the way they are learning.

Let’s talk about the amount of work first.   I saw very few kids out and about any time of day except commuting hours.   Basketball courts are empty, even on weekends.   Where are all the kids?  They are in endless cram school 补习班 classes.

A middle school child routinely gets up before 7 am and does not go to sleep until midnight or after.   Middle school students stay in school until 8 pm, and work on additional homework from 8 pm till midnight.   Younger students are often working similar hours.
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Teaching long division (除法)

I was surprised to learn that my fourth grader daughter is learning long division exactly the same way as how I was taught: a highly mechanical process that is worse than doing dishes.

Now looking back, I learned a lot of math mechanically without putting much thought into what I was doing.  Perfecting the steps as if I was self-training to be a robot.

Tomorrow I am going to show why we did long division the way we did, and why there are many other ways.

养不教,父之过.教不严,师之惰

Brenda Barnes’s advice to her children

Every advice in this list is important and should be read them often.

1.  Work hard and do good work.
2. Value family. They will always be there for you. You may have tiffs, but work at keeping a healthy relationship.
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My new best friend

A young skinny girl wearing goggles approached me in the pool. After a few seconds of staring at me, she said to me “who are you?”
Startled by the question from someone who looked less than ten years old, I hesitated while maintaining a smile and asked her to repeat her words.
“Who are you?”
Now the question is clear and I had to respond. “I am a swimmer.” I said.
“Oh” she seemed to have been delighted whereas I was mystified.
“You know, yesterday in the shower. I am sorry that I took a long time.”
Now I remember. Yesterday after family swim a lot of people were waiting in line for shower. For some reason her shower took a long time. The wait was so long that my very good-natured and patient children began to look like they wanted to go home. I finally lost patience and began telling whoever in the shower to speed up. And I repeated my demand with increasing volume.
Now that I remember who she is. I smiled genuinely “oh I am sorry that I shouted at you.”
After a few seconds of thought over my apology, she said “are you sure that you were patient enough? you know you should not be shouting”
…, …
We held quite a long conversation right in the water. In the end we both were content with the knowledge that each of us is a reasonable and good human being.

We now are friends. I almost feel that she is a very good friend because we can reason with one another, even though she is eleven.  I think the feeling is mutual.  Because she just asked me to help her find her lost earring from the deep big pool.

Financial math equations

  1. Revenue – Expense = Profit,
  2. Net worth= Asset – Liability

My dear children learned while we were shopping at IKEA that:

Revenue & Expense by Elizabeth

Revenue & Expense by Elizabeth

  revenue = money coming in  expense = money going out

  profit = revenue expense

Money that mommy earns from her work is revenue

Apartment rental income is revenue

Money we spent paying for everything we use is expense

  asset = things that bring in profit

  liability= things that do not bring in profit

Can you please tell me what are the assets and what are the liabilities that you know?

Let kids learn about money and finance 钱

Money (钱)is very important in life, although it is quite pointless to compare it with things that are best not to be measured in money.   Money is money.  It does what it does.  It is very important.  Period.

I ask my children “If you have $100 and you spend $100.  How much do you have left?”  “Nothing left”.   “Likewise, if you have $1,000,000 and you spend $1,000,000.  How much do you have left?”  “Zero!”

That is right.  To be rich, it is not only important that one needs to make money, but also save money (节省).   My children know that we should buy things on sale as much as possible.

We were looking at historic prices of properties in Zillow.com.   I showed them the time series of prices and point to the trough in 2009 “this is sale price” and the peak in 2005 “and this is the full price that we should never pay for. “

When we go shopping, I try to let my children pay.   Before we come to the cash register, if our shopping cart is not that full, I will ask them to try to sum up how much the total is and compare how close our calculation is to the actual.

There are just so many places and so many things to learn.   I have explained to my children what a bank does, interest rate, what collateral means and so on.   “Why do you think the bank employees are so nice to us by giving us candies/hot chocolate when they are helping us to keep our money?”