Topic, Math Whiz Quiz Game V2

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demonicyoshi 11 years ago

V=L*W*H
12,000=(x)*(3x)*(4x)
12,000= 12x^3
1,000=x^3
x=10

Ferrari12 11 years ago

New question!

nelson90 11 years ago

The number of combinations is
C(61,3)=61*60*59/(3*2)=35990

Ferrari12 11 years ago

Still one question left to answer!

SimonM 11 years ago

f(3)=27-9k+3+6=0
36=9k
k=4

Ferrari12 11 years ago

Correct :)

SimonM 11 years ago

Woops, I forgot there was already a '-4' So the 5 should be 9... so the radius is 3...

Ferrari12 11 years ago

That's not what I, my teacher and WolframAlpha get ...

SimonM 11 years ago

(x^2-2x+1) - 1 + (y^2-4y+4)-4 = 0
So (x-1)^2 + (y-2)^2 = 5.
The radius is sqrt(5) and middlepoint (1, 2).

Ferrari12 11 years ago

Very good, have a point :)

nelson90 11 years ago

Indeed you know, Simon, I had no doubt. I also knew it without Wikipedia, I only made a quick search on Gaussian integral, just to avoid to have to remember the solution :)
About the integral sign: maybe you could use "INT" instead, special characters give sometimes strange results.

About the question: If y>x and x^2>y^2, can x be larger than zero?
x^2>y^2 ==> x^2-y^2>0 ==> (x+y)(x-y)>0
y>x ==> x-y<0
(x+y)(x-y)>0 and x-y<0 ==> x+y<0 ==> x<-y
Since x<y and x<-y, x cannot be larger than zero.

SimonM 11 years ago

I know Nelson, I wondered if someone would know it without wikipedia or such. (I do :))
@Ferrari: BL screwed up my integral signs.

nelson90 11 years ago

@Simon: this integral is known as "Gaussian integral", some demonstrations can be found on Wikipedia:
Wikipedia Gaussian integral

Ferrari12 11 years ago

What are the wierd signs for? (Ã¢^ etc.)

SimonM 11 years ago

A bonus question for fun:
Show that âˆ«(-inf,inf)[e^(-x^2)]dx=sqrt(pi).
(Where âˆ«(a, b)[f(x)]dx is the integral of f(x) to x from a to b. inf = infinity)

nelson90 11 years ago

The volume of a sphere is equal to 4/3*Pi*r^3. Then, the volume of sphere B is 2^3=8 times the volume of sphere A.

Ferrari12 11 years ago

Still one question left to answer :)

nelson90 11 years ago

2. (2x^2*e^(x^2-3x))'
= 2(2x*e^(x^2-3x)+x^2*(2x-3)*e^(x^2-3x))
= 2*e^(x^2-3x)*(2x+x^2*(2x-3))
= 2*e^(x^2-3x)*(2x+2x^3-3x^2)
= 2x*e^(x^2-3x)*(2x^2-3x+2)

Ferrari12 11 years ago

New questions :)

gameinsky 11 years ago

10 - 1 = 9

nelson90 11 years ago

C(n,p) is the number of different possibilities to choose p objects among n. It is equal to n!/p!/(n-p)!

Ferrari12 11 years ago

I didn't think about that, because in Norwegian it's always a wovel. Obviously I therefor got a different answer, but yours is correct too :)

But what is C(5,3)?

SimonM 11 years ago

Yah, that's what I was doubting about, because it is a vowel and consonant. :)

nelson90 11 years ago

@Simon: in French, "y" is a wovel, but in English "the letter Y can be a vowel (as in the word "cry" or "candy"), or it can be a consonant (as in "yellow")" (found on Wikipedia).
So you answer is correct with your assumption :)

SimonM 11 years ago

Do you count 'y' as a vowel?
If not I think 21*20*19*5*4=159600 is the answer. :)
(probably not right).
edit:
I forgot to multiply with C(5,3) which is 10
So my answer is 1596000

Ferrari12 11 years ago

Correct! :)

SimonM 11 years ago

We first scale down the problem to work with percentages. We can easily find the equations of the runners.

James:
| y = x from 0 to 1
| y = -x+2 from 1 to 2

Suppose t is the time when John reaches the given place and v is the speed of James, then (7/4)*t*v=1100 thus t=(4/7)*(1100/v). So we know the equations for John

John:
| y = (4/7)x from 0 to (4/7)
| y = -(4/7)x+(8/7) from (4/7) to (8/7)

So now we find the intersection of the lines:

x = -(4/7)x + 8/7 so (11/7)x = (8/7) so x = (8/11).

This is the percentage of the distance 1100. So the distance from the starting point to where they meet is (8/11)*1100=800

Ferrari12 11 years ago

New question! :)

Better late than never, I hope.

Ferrari12 11 years ago

Nelson (regarding the cake), the glazing may be more expensive than the cake, but it is the best part :)

Regarding the Extra question, I think I understand. Thanks for the help! The reason I asked was that today I had a maths test, and on the test, there was a problem which we have never learnt how to solve, so our teacher came up with a replacement task. This was part b) of that task, and rather annoyingly, I have never learnt how to solve problems like these neither. After all, my guessing wasn't too far off, but I forgot that the variables were independent and thus did not get the correct answer. :/ I just hope that task doesn't count for much!

I'll come up with some new tasks tomorrow :)

SimonM 11 years ago

I think we simultaneously posted :)

[<<] [1] [2] [3] [4] [5]

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 â†’ 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

SPOILER

Topic, Math Whiz Quiz Game V2

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