Category Archives: Mathematics

Math homework

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I will let you in on a little secret: I love doing math homework. Always have, always will. I love the process. I love reading the problems, thinking of solutions, and checking the questions off one by one. Even when it’s easy, it’s still fun.

Just for fun I’ve gone back to my old high school math textbooks. I’m skipping years 7 and 8 and starting with year 9. Then I will do 10, 11, and 12, at the highest level.

At the moment I’m working through Australian Signpost Mathematics New South Wales 9 (5.1-5.3) Student Book, which is the year 9 textbook. I’m only up to page 10, fractions and ratios. I should work on it more than I do. Let’s see what I can do about that. :)

The most difficult math problem in this year’s HSC

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The “HSC” in Australia is the “High School Certificate” which you get when you graduate high school. In order to do that you have to take the final exam, known as the “HSC exam”, or simply the “HSC”.

When I did the HSC 24 odd years ago the top level maths course (which I took) was called “4 Unit Maths”, whereas these days the top level course is now called “Maths Extension 2”. I expect the difficulty increased over the decades too.

Here’s the hardest question from this year’s Maths Extension 2 HSC paper:

There’s an article about it all in the newspaper today: ‘Not seen a question like it’: The most difficult problem in this year’s HSC.

I don’t remember enough about complex numbers, geometry, and trigonometry to answer this question, it is quite beyond me.

In The Lab With Jay Jay – July 28, 2023 – Testing Riden RD6006 with 19.5V power supply

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This post is part of my video blog: In The Lab With Jay Jay.

Today I confirmed I can successfully power my Riden RD6006 power supply with this 19.5V AC adapter I picked up from Amazon. Big thanks to my mate Rick over on the EEVBlog forum for his help with this one.

In this video I use a 100W 6Ω resistor to test my Riden RD6006 power supply at various voltages from 1V to 18V up to a maximum power of 54W.

I should note that in this video I tried to draw 54W of power from the power supply, but the power supply is only rated up to 45W so I probably shouldn’t have done that, and won’t have any reason to ever do that again, I was just testing the maximum. So maybe don’t do that at home. :)

CRC

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I watched Ben Eater’s videos How do CRCs work? and Checksums and Hamming distance (the full course is Learn about error detection) then found the Wikipedia page: Cyclic redundancy check.

Also of interest:

Keyspace on the back of an envelope

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One question that always plagues me: should I use 32-bit or 64-bit keys. I can never make a firm decision on this point. But I’ve just done some back of the envelope calculations in thinking about it.

If you issued one identity per second, every second of every day, it would take 136 years to exhaust the keyspace.

If you issued one thousand identities per second, it would take 50 days to exhaust the keyspace.