2u Mathematics Marathon v1.0 (1 Viewer)

[blue_eye_baby]

Spoiler

integrating dV/dt = -1.92t
V = -0.96t^2+C
when t = 0 it is full V=25000
So 25000 = 0+C
Then V = 25000 - 0.96t^2

ii) 40% of full = 10000
10000 = 25000 - 0.96^t
t= 4.35, rounded to 5

Spoiler

suppose to be ii) 125 seconds.... thats the answer i have

 

[blue_eye_baby]

composite means the number can only be divided by itself and 1

eg. 7

 

[karen88]

Spoiler

integrating dV/dt = -1.92t
V = -0.96t^2+C
when t = 0 it is full V=25000
So 25000 = 0+C
Then V = 25000 - 0.96t^2

ii) 40% of full = 10000
10000 = 25000 - 0.96^t
t= 4.35, rounded to 5

how did u get 4.35.... i got 125

 

[chin music]

composite means the number can only be divided by itself and 1

eg. 7

Na u got it the wrong way round. Thats a prime number. Composites the opposite it means that its factorable.

 

[lie_stella]

Spoiler

suppose to be ii) 125 seconds.... thats the answer i have

uh oh yea.. wrong in pressing the calculator in chronological order.. -_- in suppose to 125

 

[lie_stella]

Na u got it the wrong way round. Thats a prime number. Composites the opposite it means that its factorable.

i thought it prime number..

 

[karen88]

chin music was rite... composite no. is any no. which is not a prime no.

 

[chin music]

Next question

A fish farmer began business on 1 January 1998 with a stock of 100 000 fish. He contract to supply 15400 fish at price of $10 per fish to a retailer in December each year. In the period between January and the harvest in December each year, the number of fish incereases by 10%.

When will the farner have sold all his fish and what his total income will be?

Spoiler

Ahhh i was thinking so complex but it was so simple. Since he gives off 15400 fish a year and since it takes him 11.5 years then the number of fish is 11.5*15400 and the number of money is that *$10. So its $17710000

 

[chin music]

^^How do u figure?

 

[blue_eye_baby]

Spoiler

Ahhh i was thinking so complex but it was so simple. Since he gives off 15400 fish a year and since it takes him 11.5 years then the number of fish is 11.5*15400 and the number of money is that *$10. So its $17710000

man im screwed

 

[karen88]

Question #X:
20 cards, labelled 1 to 20, one card is chosen, find the probability that its number is composite or >12.

whats da answer to this question...

Spoiler

i got 3/4?!?!?!

 

[blue_eye_baby]

^ answer is

Spoiler

8/20 + 11/20 - 6/20
=
7/10

 

[karen88]

^

Spoiler

what were u no. i had 1,4,6,8,9,10,12,14,15,16,18,20

 

[MarsBarz]

A composite number is a positive integer which is not prime. Note that 1 is neither a prime number nor a composite number (at least that is what I gather).
The first few composite numbers are 4, 6, 8, 9, 10, 12, 14, 15, 16...
You can find more about composite numbers at mathworld.

So herein is the answer to the question which I posted:
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20
P(composite) = 11/20
P(>12) = 8/20
P(composite and >12) = 5/20
Therefore:
P(composite OR >12) = P(composite) + P(>12) - P(composite and >12)
P(composite OR >12) = 11/20 + 8/20 - 5/20
P(composite OR >12) = 7/10
And that is the final answer.

 

[chin music]

^

Spoiler

what were u no. i had 1,4,6,8,9,10,12,14,15,16,18,20

1 isnt a composite number, 17 is greater then 12, 13 is greater then 12 and 19 is greater then 12. that makes 14/20=7/10. meh screw the spoiler ppl trying to do this question will be 2 pages back

 

[sunjet]

composite question

Spoiler

7/10

edit: fucking capped takes too long to load ;p

 

[chin music]

Haha this has been like the easiest question in the whole marathon but its gotten the most attention

 

[karen88]

ohhhh ok... cos i counted da 1 as well... for composite... thats why i had 12/20 + 8/20 - 5/20...... therefore = 3/4

 

[[Damo]]

since probability is non-mutually exclusive; ie: P(A or B)= P(A) + P(B) - P(A and B)
Hence; P(>12 and composite)= P(8/20) + P(11/20) - P(5/20)
= 7/10

(composite: opposite to prime)
(u myte wanna check this)

 

[MarsBarz]

Lol didn't realise my probability question would get 2 pages of attention. As I've said before, the answer is 7/10 and I have posted the full solution above.

Next question:
Solve the equation sin2x=sinx for -PI<=x<=PI