Quote:My 6th grade granddaughter has always and continues to struggle with math. It has always been a hole in my education as well. However, I did learn arithmatic and figured I ought to be able to help her from time to time. The other day she brought home a problem which was "express the mixed number 8 1/3 as a percent". My wife and I both immediately answered 8.33 percent which is what my granddaughter had answered. Apparently the correct answer was 833 percent. I remain confused as to what I am missing here. I must be assuming something not in the question. Anyway, I guess I cannot be counted on to be of much assistance to her. Also, her district uses the connected math curriculum which apparently eschews teaching kids to learn how to calculate things manually etc. Bah!

Quote:Hi,
As to the teaching of math, in general, it is done very poorly. Many who teach it don't really understand it themselves. And what is taught is often the basics to become a mathematician rather than the general knowledge (and ability) needed by the average person.

The specific problem you lay out hinges on the definition of 'percent'. It comes from the Latin, and can be translated as 'parts per hundred'. So, 1 percent (1%) is one part in a hundred or 1/100 or 0.01. A 100 percent is 100 parts per hundred, or 100/100 or 1.

Now, since 100% is the same as 1, then 8 is the same as 800% by simple ratio. Then 1/3 is (approximately) 33/100 and so 8 1/3 is 833% (more correctly, since 1/3 is a repeating decimal, it is 833.33...%)

Hope that helped.

--Pete

Quote:It did. Thanks:)

Quote: Also, her district uses the connected math curriculum which apparently eschews teaching kids to learn how to calculate things manually etc. Bah!

Quote:Sometime you may not have your calculator, or cell phone, or whatever it is they use these days to figure 2 + 2.

Quote:Sometime you may not have your calculator, or cell phone, or whatever it is they use these days to figure 2 + 2.

Quote:I think someone posted a story on the Lounge about a guy who got a quote for internet service at something like 0.33 cents for a certain amount of bandwidth. Then he was charged 0.33 dollars per unit when the bill came. The service provider in that case has made the opposite mistake that you made. They see the value less than one, and assume it is a fraction of the whole, when it is a fraction of the percentage. You saw a number greater than one, and assumed it was already meant to be the pennies. It was in fact the dollars and the problem is to convert to cents.

Quote:A funny thing happened when I was a senior in high school. I forgot to bring my calculator on the day of a physics test. Besides long division and multiplication, part of solving the problems was to take trig functions and punch them into your calculator. I didn't have my calculator. :ph34r: I worked the problems to the end with the trig functions still in the answer. Then, being way to smart for my own good when I was 18, I *estimated* the decimal equivalent of the trig functions in my head and put it behind one of those squiggly equals signs. :lol:I came close enough that when the science teacher handed back my graded test, he looked at me as if I had just beamed down from the Enterprise. Lot of good this stuff does me now that I work in shipping. :lol:

Quote: . . . sin(pi/4) = cos(pi/4) = 0.7170 . . .

Quote:I just went about memorizing certain values. Like sin(pi/4) = cos(pi/4) = 0.7170, sin(pi/3) = cos(pi/6) = 0.8660, and sin(pi/6) = cos(pi/3) = .5 (then used the various mulitples of those around the circle by remembeingr what the sign of those trig functions were for each quadrant, so quad 1 = positive, quad 2 sin pos, cos neg, quad 3 both neg, quad 4 sin neg, cos pos). Then it just becomes a quick memorization of tan, cot, sec, and csc (sin/cos, cos/sin, 1/sin, and 1/cos) and doing that math quick in the head.

Quote:I just went about memorizing certain values. Like sin(pi/4) = cos(pi/4) = 0.7170, sin(pi/3) = cos(pi/6) = 0.8660, and sin(pi/6) = cos(pi/3) = .5 (then used the various mulitples of those around the circle by remembeingr what the sign of those trig functions were for each quadrant, so quad 1 = positive, quad 2 sin pos, cos neg, quad 3 both neg, quad 4 sin neg, cos pos). Then it just becomes a quick memorization of tan, cot, sec, and csc (sin/cos, cos/sin, 1/sin, and 1/cos) and doing that math quick in the head.

Quote: and -- of course -- XL.:)

Quote:I remember my VWO-level high school biology exam. I forgot my calculator.:(

Then I had to calculate the chance in percentage a heritage question, with a non-diminant gene combined with a semi-dominant gene (only in the female line) affecting the same position of the RNA chain in a a line of 8 people (4 couples), whose children would then meet, followed by grand-children, or somethign close to that. It wasn't a pretty calculation. I had to use 1,5 A4 pages. On top I noted "forgot calculator, sorry". I had it right.:D

Oh, and the best way to learn math? Ditch the calculator. I had a hardliner math teacher in my first year at high school. Everything by head, no calculators. That served me well. I still can do some decent math when I close my eyes and start calculating, faster then my mates, when we play role playing games. Dividing, adding, multiplying, etc. I'm totally worthless at cos, sin, tan, root, etc stuff though. Start->run->calc ftw. But I never use those any more anyhow.

Quote:Forty smilies??

Quote:A funny thing happened when I was a senior in high school. I forgot to bring my calculator on the day of a physics test. Besides long division and multiplication, part of solving the problems was to take trig functions and punch them into your calculator. I didn't have my calculator. :ph34r: I worked the problems to the end with the trig functions still in the answer. Then, being way to smart for my own good when I was 18, I *estimated* the decimal equivalent of the trig functions in my head and put it behind one of those squiggly equals signs. :lol:I came close enough that when the science teacher handed back my graded test, he looked at me as if I had just beamed down from the Enterprise. Lot of good this stuff does me now that I work in shipping. :lol:

Quote:You are still left with the question of does .02 cents = $.02?

Quote:Or memorize the Taylor expansions, they're not very complicated for sin and cos.