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#3 Re: Maths Teaching Resources » Maths Books » 2016-12-06 00:50:03

I only point them out because they are excellent for keeping in shape. I do them.

#4 Re: Maths Teaching Resources » Maths Books » 2016-12-04 23:41:34

Hmmm, how about ganesh problems?

#5 Re: Help Me ! » Minimum surface area » 2016-12-04 19:19:16

Okay, post when you get another one or when you are ready to see how to do it.

#6 Re: Maths Is Fun - Suggestions and Comments » More Topics Need » 2016-12-04 19:18:32

Coordinate Geometry and Analytical Geometry are the same thing.

#9 Re: Help Me ! » Minimum surface area » 2016-12-04 13:31:13

Hi;

You can get right answer with your S = (6561 w^3 + 917000)/(2025 w) but my S = 36680/(81 w) + (81 w^2)/25 is a bit easier too look at.

Either way you now need to minimize S. That will involve the derivative. If you do not know what that is then we can minimize using iteration but that might be confusing also. There might be another way using the AM-GM inequality but that too would be confusing.

Looking at the book you are using that fellow uses a graphic calculator on his earlier problems. You are trying to do the problems without one of those? For that you will need a bit more math than you currently know. The graphic calculator way does not require you to know so much math. The pencil and paper way requires that you do.

#10 Re: Help Me ! » Algebra Problems » 2016-12-04 13:21:30

It is not necessary. You have the correct answer. Until someone can come up with another polynomial that works too why bother?

#11 Re: Help Me ! » Algebra Problems » 2016-12-04 08:54:40

It was all ironed out for you over in another thread.

#12 Re: Help Me ! » Minimum surface area » 2016-12-04 08:53:34

What did you get for an answer? Did you get 164.91 for the minimum surface area?

#13 Re: Help Me ! » Minimum surface area » 2016-12-04 06:37:27

Hi;

A) S = 2*h*w + 2 l*h + 2 w*l

Using the fact that h = (81 / 50) w we substitute and get

B) S = (131 l w)/25 + (81 w^2)/25

Solving for l in l*w*h = 140 we get

l = 7000/(81 w^2)

Substituting that into B) we get:

S = 36680/(81 w) + (81 w^2)/25

Now all you have to do is set the derivative of that equal to 0 and solve for w. What do you get now? The problem with this approach is that you will have to solve a cubic. Easy for a computer, hard for a human. And, 4.12 is correct for w rounded to 2 decimal places.

#14 Re: Help Me ! » Minimum surface area » 2016-12-04 04:15:56

Hi;

You need to minimize the surface area 2(hw)+2(lh)+2(wl) subject to the constraints that lwh=140 and h=1.62w. This leads to a definite answer.

Oh and by the way, people see the legendary Sasquatch here often. It goes by the name Skunk Ape. No one really knows what the creature eats. Speculation says, it will grab a gator and snap it into two pieces as effortlessly as we could a twig. Others believe it kills bears for its grub. The darker side people think he will eat a human when it can. Nobody, but nobody, thinks it eats cereal.

#16 Re: Maths Teaching Resources » Maths Books » 2016-12-03 22:11:13

Hi;

Just so I know what your aptitudes and capabilities are, I will ask a question. Do you know what Geogebra is?

#18 Re: Help Me ! » I don''t understand the steps in this solution. » 2016-12-03 21:19:10

There are 30 of each in the tens place but each of them is multiplied by 10 because a 5 in the tens place is 50. He could just as easily said 30(10+20+30+40+50+60+70).

#19 Re: Computer Math » Triple Summation » 2016-12-03 13:49:57

No, there was more than that but zeta(3) was part of the conjectured form.

#20 Re: Help Me ! » I don''t understand the steps in this solution. » 2016-12-03 11:14:56

Hi;

There are 7 x 6 x 5 = 210 total ways to arrange the numbers 1 to 7 in groups of 3. So in the ones digit there will be 30 ones, 30 twos, 30 threes etc. He just adds up all the numbers in the first column which will be 30(1+2+3+4+5+6+7). Is it clear now?

#22 Re: Help Me ! » Algebra Problems » 2016-12-03 10:52:25

Part 2... I do not know how.

#23 Re: Coder's Corner » Comparing percentile by python or numpy with the definition » 2016-12-03 07:00:20

In regards to your previous question.

There are at least 9 different definitions of empirical quantiles.

So both numpy and Mathematica etc are correct, depending on what definition the textbook is using.

Is 100 percentile possible? I think theoretically no

I would think that 100 percentile would mean the value that 100 percent of the data would be less than. But some definitions obviously include equal to also. I have seen many cases of 100 percentile computed and urge you to look at this answer:

http://math.stackexchange.com/questions … tile#33502

whuber, is an expert on statistics and he seems to indicate 100 percentile is allowed.

#24 Re: Help Me ! » Algebra Problems » 2016-12-03 06:47:22

The fact that Remainder equals zero means that f(x) | g(x).

#25 Re: Help Me ! » Algebra Problems » 2016-12-03 05:43:37

This one.

Yes, I got 6x^5-15x^5+10x^3
Thanks!

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