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In the discussion thread: 4th/5th Grade Math Advice Needed [View all]

Response to PBC_Democrat (Original post)

Sat Apr 10, 2021, 10:22 PM

10. Hah...I feel bad for my eight year old son. It's not good to have a dad who is a math PhD.

I tell him that I hope he is better at math than I am. No pressure of course! LOL

The way I get him to tolerate my crap is by letting him use the Oculus only if he does math with me.

Heís not bad, but definitely no Terence Tao or 1% of Tao.

I was able to get him to understand why summing from 1 to n is n(n+1)/2.
If S is that sum then:

S = 1 + 2 + 3+...+ (n-1) + n
and in reverse order
S = n+(n-1) +...+ 2 + 1

Adding both rows, you get each column adding to n+1 on the right and there are n of those.

2S = (n+1) + ... + (n+1) = n(n+1) and dividing by 2 gives us
S = n(n+1)/2.

The story for the above is that 8 year old Karl Friedrich Gaussí class got into trouble and was given the rote exercise of adding the numbers from 1 to 100. He had the answer in less than a minute because he came up with the above proof and gave the correct answer of 5050. She recognized that Gauss was gifted at that point (geez ya think?!).

They didnít do that in class, but I thought it could be understood (I wanted to teach him mathematical induction which I havenít gotten to, because he gets annoyed. This would be a good easy example to use induction on for an alternative proof. It wouldnít be as constructive by induction though because you need to know the result a priori).


They just started fractions in school, but they are taking a month to do what I explained in an hour. I really donít know why. The reason I wanted to do induction was so I could prove the prime factorization theorem to him which is almost trivial by induction. That would be useful for understanding reducing fractions by canceling common primes in the numerator and denominator.

I was able to teach him about getting common denominators and I explained least common multiples, but not how to get the least common multiple efficiently. Prime factorization helps a lot there actually. He knows how to add fractions now by getting common denominators, but I havenít done reducing fractions yet.

He gets most of the concepts, but doesnít really love math, so I definitely need to back off a lot or heíll hate me! In school he doesnít always ace the math tests (usually gets one question wrong, but he always tells my wife, ďdonít tell daddy!Ē). It is almost always due to the fact that his language comprehension is atrocious and the problem was too wordy and not just straight pure math.

Maybe this can jog your mind for a few ideas.

I canít wait until my son finally gets to more interesting math so I can really show him good stuff. I think calculus is a bit overrated. I think they should do linear algebra in high school instead. That is huge for statistics and modern applied math often used for data scientists and machine learning practitioners that are more and more in demand every day. Being good at multivariable calculus absolutely requires strong linear algebra. I wish that was emphasized to me before grad school! It would have saved me from some hassles! Got Carried away obviously...

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Arrow 10 replies Author Time Post
PBC_Democrat Apr 2021 OP
SheltieLover Apr 2021 #1
madaboutharry Apr 2021 #2
PoindexterOglethorpe Apr 2021 #3
Karadeniz Apr 2021 #5
BigmanPigman Apr 2021 #4
Buckeye_Democrat Apr 2021 #6
soothsayer Apr 2021 #7
eppur_se_muova Apr 2021 #8
Tetrachloride Apr 2021 #9
LineNew Reply Hah...I feel bad for my eight year old son. It's not good to have a dad who is a math PhD.
Lucky Luciano Apr 2021 #10
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