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The very first test case is wrong. Puzzle description clearly explains that the answer is â€ś1:3â€ť while the answer inside the example AND the test case is â€ś1:2â€ť.

So the ratio P(A) : P(!A) is 1:2 (read 1 to 2).

I see an explanation, why the answer is 1:2 there.

Hi there,

Stats are really not my cup of tea. I have a problem with â€ś4-Ultimate testâ€ť (and also test 5 but I would at least understand what is wrong with this one)

I tried to stick as much as possible to the concept of taking balls out of the bag.

I think I got a decent algorithm but I might be totally wrong.

Test 4-Ultimate test

inputs:

n=30 total nb of balls

w=10 nb of white balls

s=10 total nb of balls extracted

k=5 nb of white balls to be extracted

I get the following result

P(A)= 10 / 30 (white ball)

x 9 / 29 (white ball)

x 8 / 28 (white ball)

x 7 / 27 (white ball)

x 6 / 26 (white ball)

x 20 / 25 (black ball)

x 19 / 24 (black ball)

x 18 / 23 (black ball)

x 17 / 22 (black ball)

x 16 / 21 (black ball)

P(A)= 5168 / 10015005

P(!A)= 10009837 / 10015005

result: 5168:10009837

expected: 62016:414889

I donâ€™t see what is wrong: is it my fraction simplification or the way I compute the stats ?

Any help will be greatly appreciated !

Itâ€™s also possible to draw the black balls before the white (or in any other order like WBBBWBâ€¦), you only count one.

1 Like

Hello this post makes me understood my error for the ultimate test 1

now i have 80 % and the ultimate test 2 that failedâ€¦

I canâ€™t undestand my error since the result a nearly similary

60 balls

40 whites

50 balls taken

35 proba 35 whitesâ€¦ ?

i Do

2250829575120 * (C 50 35)

40/60* (white balls)

39/59*

38/58*

37/57*

36/56*

35/55*

34/54*

33/53*

32/52*

31/51*

30/50*

29/49*

28/48*

27/47*

26/46*

25/45*

24/44*

23/43*

22/42*

21/41*

20/40*

19/39*

18/38*

17/37*

16/36*

15/35*

14/34*

13/33*

12/32*

11/31*

10/30*

9/29*

8/28*

7/27*

6/26*

20/25* (blacks balls)

19/24*

18/23*

17/22*

16/21*

15/20*

14/19*

13/18*

12/17*

11/16*

10/15*

9/14*

8/13*

7/12*

6/11

my result

1235750079647531:7896812518143536 => 0.15648719996

expected result

134976:862537 => 0.15648719997

i canâ€™t undestand why those result are so closed if i m wrong

any clue will be very lovely !

thx

I use Windowâ€™s Calculator to do this division, got

0.15648719996939269532056443461388

So the last few digits are 9997 when simplified to the same number of digits as yours.

1 Like

yes but i canâ€™t undestand the ratio found (134976:862537) compared to mine, how the result could be so much factorized

There could be a loss of precision in the middle of your calculation.

What language are you using?

What data type are you using to do the calculation?

2 Likes

I use javascript,

I only do the multiply on the numerator and denominator;

Then i m looking for the largest common divider and divide allâ€¦

I m not sure to lose precision using multiplyâ€¦ but you may be right

You could try using BigInt to verify the result. The correct fraction should be able to be reduced to two smaller integers.

2 Likes

You are the winner, is use BigInt() for javascript and it works nowâ€¦

Thx you @java_coffee_cup !

1 Like

I have success on all test cases â€“ so efficiency is now OK. I fail on validator 2.

As far as I can tell, Iâ€™ve dealt with all divide by zero cases so I donâ€™t think Iâ€™m generating an error.

Would appreciate some guidance on where to look/what to improve.

Thanks!