Topic, Math Whiz Quiz Game V2

  That's way too low. I'll write the question in a different way: How much will it cost you to buy so many lines that you are guaranteed that one of your lines are chosen in the draw.

  28.9 NOK? *Thinks I'm wrong but whatever*

  Again, Nelson wins. You other guys need to give him some competition!

  63=9*7, 64=8*(6+2), 65=5*(4*3+1)

  20=4*5,21=3*7,22=>1,23=8+9+6

Well, I got 4...

  Those are all correct answers, you are building up quite a lead here, Nelson.

Psychomaster: As you are only nine years old, I wouldn't expect you to be able to answer most of these questions either. In fact, the majority of them are based on the curriculum of 10th to 12th grade in Norway. So taking age into concideration, I wouldn't say that you are all too bad. For all I know, you could actually be very good. So cheer up :)

  I suck at math.. Lawl (yet in school math is my best subject..)

  1) a parenthesis is missing, I suppose you meant (X^2/(X-1))'
(X^2/(X-1))'=(2X(X-1)-X^2)/(X-1)^2
=(2X^2-2X-X^2)/(X-1)^2 =(X^2-2X)/(X-1)^2
=X(X-2)/(X-1)^2

2)
((x-1)^2)'=(x-1)^2
2(x-1)=(x-1)^2
2(x-1)-(x-1)^2=0
(x-1)(2-x+1)=0
(x-1)(3-x)=0 ==> x=1 or x=3

3)
I z^2/2y=z/((x+1)^2)
II x=y-2/z
III y=x+z^0

z not equal 0, y not equal 0, x not equal -1

I z^2/2y=z/((x+1)^2) ==> z(x+1)^2=2y
II x=y-2/z ==> z(x-y)=-2
III y=x+1 ==> x-y=-1

from I and III: zy^2=2y ==> zy=2
from II and III: z(-1)=-2 ==> z=2
then y=1, x=0

4)
Eight years ago, Peter was twice as old as George ==> P-8=2(G-8)
Today, the sum of their ages equals 28 ==> P+G=28
P=2G-8
2G-8+G=28 ==> 3G=36 ==> G=12
P=2G-8 ==> P=16

  Nelson got it again :)

  Since (...)^0 is equal to 1, the result is 2

  .. 1 point for that?.. Wtfidunevenlolwat

  You might be right on that Nelson, I just did some quick calculations, and I haven't double-checked them.

Regarding the current question, Gameinsky posted the correct answer. This situation is actually known as The Monty Hall problem, and there is an article on Wikipedia explaining it further, if anyone's interested. Monty Hall porblem

[edit] New question is up!

  @F12: just coming back to your function. I think that X=-1/4 cannot be a solution of equation
6X-3/(4sqrt(X))=0
because the square root of a negative number is a complex number, and 6X is a real number.

About the new question: I would say 50% of winning the car, whatever the door you choose.

  It's better to switch because in the beginning you had 33% chance to get the car, the host knows which door has a goat, so there's a 100% chance that door has a goat, your door has 33% chance to get the car, the other door 0%, so the remaining 66% has to be in the other door. So yes, switching to the other door gives you more chance (doubles it basicly)

  I heard that question before. About 33.3% chance no matter what door.

  Thanks F12. In that case, the answer is X=0.25

@Simon: yes, there is a standard way to solve equations of degree 4. For that, you will have to solve first an equation of degree 3, and there is also a standard way. It would be a bit long to explain that in details.

  In question 2 I may have used an unprecise term, I just translated the Norwegian one into English using "commons sense". What I meant with, when the graph is turning is when does f ' '(X)=0. In Norwegian we call that "the turning point", but it may have a different term in English.

Here's I worked it out, it may be wrong, but hopefully not :)

And Simon, you need to read the text more carefully. Yes, there are indeed 13 fruits left in the basket, but I only have the 5 I took out :) (If you think the question is stupid, don't blame me, I got it from an actual 10th grade maths class.)

[edit] Now that I've given you the answers, I better come up with some new questions :)

  Thanks Simon for the information. Until now, I didn't find a way to solve this equation, I will try again.

Just one thing: by squaring both members, you have introduced 2 additional solutions (the equation you are solving is of degree 4). The original equation is not 0 for X=1.07191. The other solution is about -1.291

  He meant a local minimum/maximum. So when the first derivative is 0, plus the first derivative has to change sign.

Solved with wolfram after reducing the equation to 36x^4 -120x^2 -9x+100 = 0
x = 1.07191 and x = 1.51035
Both are approximations.

There is no standard way to solve a polynomal of degree 4 if you don't know one zero point.

  What do you mean by "the graph turn"? If it is an inflextion point, it occurs when the second derivative is 0, for X=0.25

  Ok a local maximum/minimum:
f(x) = x^3 -5x + 3 - sqrt(x^3) = x^3-5x+3-x^(3/2)
f'(x) = 3x^2-5-(3/2)x^(1/2) =3x² - 5 - 1.5sqrt(x)
f'(x)=0 -> x=... annoying

Edit: use / for division instead :

  Your formulas have weird stuff in it, it's probably the BL make up.
Btw: with turning a function you mean when it's 0, or a minimum/maximum, or an inflextion point?

Btw: 13 fruits left and you have 5 fruits. :)

  New questions released :)

  Correct answers!

New questions tomorrow.

  - since (lnX)'=1/X and X^(1/2)=sqrt(X), the solution is X=1

- the distance from a corner of a rectangle to the center is the half of the length of the diagonal: sqrt(6^2+8^2)/2 = sqrt(100)/2 = 5 cm

- 4^4-7*2 = 256-14 * 242

Note: sqrt stands for square root

  Er..
Dunno first question, so gonna guess.. X=4 as I used the Power Symbol example, so 2 1's=2, so 2 2's equals 4
2nd: 7 cm? (dunno that one either, taking a possible guess) Added up north and west centimeters, got 7 CM

3rd: 2 4^4=16, 7*2=14, 16-14=2

  I thought I'd be fun to revive this little quiz-topic, orginally done by AK, who unfortunately is no longer active. The rules are more or less the same as in the old version, but if you are not familiar with them, here is how the game works:
- I post maths questions, and then it's up to you guys to find the answer(s), preferably with some kind of explanation.
- The first to post the correct answer, gets the points.
- The number of points any question gives, is stated along with the question itself. Few points → Easy question, and oposite.
- New questions will be added whenever the previous one(s) have been answered correctly.

CURRENT QUESTION(S):

What is the average score of Math Whiz Quiz Game V2? (1p)

LEADERBOARD:
Nelson90: 72p
SimonM: 46p
Jim674: 7p
Gameinsky: 3p
PineappleDude: 3p
Demonicyoshi: 1p
Psychomaster: 1p
Treazer: 1p

Signs explanation