Interesting video

[Dr_Fwd]

Anyone knew this before? Video (http://www.youtube.com/watch?v=F6m2w8yh_lQ&feature=player_embedded).

[SA Friday]

Nope. I had the $10 for a TI-30 calculator...

[Irving]

I've seen that technique before, but wouldn't remember it.

I'm generally pretty bad at math and the only trick I know is how to multiply numbers by 11. Basically you just add the numbers together and put the sum between the two numbers. If they add up to more than 9, then you carry the 1 to the front number.

25x11 = 2+5 = 7
25x11 = 275

58x11 = 5+8 = 13 (carry the 1 to the 5)
58x11 = 638

If you have three numerals, it goes like...

123x11 = 1353 (starting from the last number, going right to left)
3 is the last number.
5 is the sum of 2+3.
3 is the sum of 1+2.
1 is the first number.

If one of the sums goes to two digits, carry the 1 to the number before it, BEFORE you do the next sum.

365x11 = 4015
5 is the last number.
1 was the sum of 6+5 (you get 11, carry the 1 to the 6 and leaves the 1).
0 was the sum of 3+7 (you get 10, carry the 1 to the 3 and leave the 0).
4 was the first number plus the carried 1 (3+1).

Man that is hard to explain in text. Sorry if it is confusing.



SA Fri: When I was in high school, they told us to buy the TI-80 and it cost $80.

[Colorado Luckydog]

My calculator says made in China, so I don't know why they would be doing that shit![ROFL1]
Very interesting though.

[SA Friday]

SA Fri: When I was in high school, they told us to buy the TI-80 and it cost $80.
I use a TI-84 Silver Edition for my college math and chemistry classes. The 83 or 84 is required, but some use an 89. I use the 84 as it has a periodic table and all of the element's atributes in it. It runs about $125-$135.

The TI-30 is my fall back calculator if the 84 glitches or basic math stuff.

[Irving]

The TI83 was banned from some tests I think.

I went and bought a comparable Casio for ten dollars less that had a 3 color screen. I felt pretty sneaky until every time I would fall behind in class trying to figure out how to make my calculator do what it was supposed to while the teacher gave the instructions for the TI calculators that everyone but me had. Maybe that's why I can't pass a calculus class.

[ToliXD]

Pretty cool. But, I still like my calculator.

[Mtn.man]

takes longer that way than in my head.....

[Dr_Fwd]

Wow, thank you! learned smthng new today. [Beer]


I've seen that technique before, but wouldn't remember it.

I'm generally pretty bad at math and the only trick I know is how to multiply numbers by 11. Basically you just add the numbers together and put the sum between the two numbers. If they add up to more than 9, then you carry the 1 to the front number.

25x11 = 2+5 = 7
25x11 = 275

58x11 = 5+8 = 13 (carry the 1 to the 5)
58x11 = 638

If you have three numerals, it goes like...

123x11 = 1353 (starting from the last number, going right to left)
3 is the last number.
5 is the sum of 2+3.
3 is the sum of 1+2.
1 is the first number.

If one of the sums goes to two digits, carry the 1 to the number before it, BEFORE you do the next sum.

365x11 = 4015
5 is the last number.
1 was the sum of 6+5 (you get 11, carry the 1 to the 6 and leaves the 1).
0 was the sum of 3+7 (you get 10, carry the 1 to the 3 and leave the 0).
4 was the first number plus the carried 1 (3+1).

Man that is hard to explain in text. Sorry if it is confusing.



SA Fri: When I was in high school, they told us to buy the TI-80 and it cost $80.

[KevDen2005]

I use a TI-84 Silver Edition for my college math and chemistry classes. The 83 or 84 is required, but some use an 89. I use the 84 as it has a periodic table and all of the element's atributes in it. It runs about $125-$135.

The TI-30 is my fall back calculator if the 84 glitches or basic math stuff.


I also had the money for a calculator, however I play tetris on my TI-86

[Graves]

I also had the money for a calculator, however I play tetris on my TI-86

Same here, only mine can view sites like this one[Coffee]

[KevDen2005]

My TI-86 definitely cannot visit sites-even this one...so I am super impressed.

[Irving]

That was the other thing about getting the Casio instead of the Texas Instruments. I never had any games. My calculator had a bunch of cool other programs built in though, that's how I learned about Mandelbrot.

Anyway, since we're talking about math, can someone help me with something?

I've never been able to figure out how to do the other half of percentage problems.

For example I know how to find the percentage of any number. Like 20% of 180 = 180x.20 = 36. So the price of a $180 product after a 20% discount would be $144.

I have a problem figuring out problems like this one:

"Including a 5% tax, you pay $170 for an item. The wholesale cost of the product is 20% less than retail price. How much did the store pay for the item?"

So you can't just subtract 5% from $170, then subtract 20% from that, because that's not the way it works. Can someone help me out with how to solve that kind of problem?

Thanks.

[Holy Diver]

that is completely retarded. How are the Chinese taking our engineering jobs when they're being taught this crap? and Yes.. out of curiosity I tried it for myself.. took 8 times as long as classic multiplication lol.

[Irving]

It's not a current method silly. It is probably ancient Chinese.

Can anyone help me with my question? Do I need to explain it better? I figure one of you programmers is good at math.

[Holy Diver]

"Including a 5% tax, you pay $170 for an item. The wholesale cost of the product is 20% less than retail price. How much did the store pay for the item?"

So you can't just subtract 5% from $170, then subtract 20% from that, because that's not the way it works. Can someone help me out with how to solve that kind of problem?

Thanks.

little soft on the old 7th grade algebra aye? heh

w= wholesale price, r= retail price
170=r*1.05 => r=170/1.05 => r=161.905
r=w*1.2 => w= r/1.2 => w=134.921

Now with that good karma under my belt somebody should be answering my DPMS LR308 problem shortly :)

[Irving]

Yes, that's what I said. The last "A" I got in math was 6th grade. I don't think your math is correct though, which is the point I was trying to make. 5% of 170 is different than X+5% of X = 170.

100 + 25% of 100 = 125.

But 25% off of 125 is 93.75.

[Holy Diver]

nope. It's correct. you answered your own question. 125% of 100 is different than 75% of 125. you are not looking for 5% off of total cost to find retail, you are looking for the retail cost that when 5% is added you arrive at your total cost.

[Irving]

I must not have looked at your math very well last night, as now I see what you did and it makes perfect sense. I for sure have a problem with algebra. Thanks for working it out.