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SimSimSalabim

Molten Core Raider
874
351
They're not teaching rounding, they're teaching estimation. Where rounding allows for an error of +/- 100, estimation (via truncation) is an error of +(0-198). So as long as the estimation is within 200, it's reasonable.

Not sure I agree with the value in actual use, but common core is about understanding abstract concepts, not efficiency.

Edit: Error for 3 digit estimation.
I don't disagree with all common core math concepts, but this one is worthless.

There is absolutely no valuable concept to be understood here. Roundingisestimation, requires the same thought/brain power, no higher understanding of numbers, and gives an estimation at least as good as this version 100% of the time, even if its just rounding to the nearest 100. This truncated shit gives you estimations that aren't even in the ballpark. 22.5% error is not reasonable. (Yes this could happen with rounding, but that isn't my point).

There is 0 reason to teach this method of estimation over the rounding method of estimation, except to fill empty space in your curriculum.



"Morty can you tell us what is 5 times 9?"

"Uhh, at least 40."

"That is absolutely...correct!"

oooo, ahhhh


250px-MrGoldenfold.png
 

Sutekh

Blackwing Lair Raider
7,489
106
I like math, can we keep talking about it? A friend of mine was having trouble in his astronomy class, I was helping him calculate the luminosity of stars and realized google has a pretty fucking in depth graphing calculator built in.

For instance if you did something like ((3.604*10^6)*(3.64*10^8))/(1.08*^-8) it would give a legit result.
 

Gavinmad

Mr. Poopybutthole
42,457
50,595
I like math, can we keep talking about it? A friend of mine was having trouble in his astronomy class, I was helping him calculate the luminosity of stars and realized google has a pretty fucking in depth graphing calculator built in.

For instance if you did something like ((3.604*10^6)*(3.64*10^8))/(1.08*^-8) it would give a legit result.
rrr_img_67138.png
 

Chris

Potato del Grande
18,298
-275
They're not teaching rounding, they're teaching estimation. Where rounding allows for an error of +/- 100, estimation (via truncation) is an error of +(0-198). So as long as the estimation is within 200, it's reasonable.

Not sure I agree with the value in actual use, but common core is about understanding abstract concepts, not efficiency.

Edit: Error for 3 digit estimation.
I posted in common core's support last time. The last time this came up it was an unothordox method again, but mathematically correct.

Estimating IS rounding, that's the method at least. I think that teaching NOT to round up on a 5 is more damaging than the value of simplifying the process by one step, because kids will think that it's right in the future. You are also failing kids who CAN estimate with proper rounding but don't know what the long winded name of the method is and how they have to ignore a rule they learned with it.