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Thread: three-digit number.

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    three-digit number.

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    Q.1. How many three digit odd numbers can be formed using the digits 1,2,3,4,5,6 and 7?

    Q.2. A five digit number is chosen at random, What is the probability that the product of the digits is an even number?

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    An Urch Guru Pundit Swami Sage thebullfighter's Avatar
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    Re: three-digit number.

    Quote Originally Posted by awais
    Q.1. How many three digit odd numbers can be formed using the digits 1,2,3,4,5,6 and 7?

    Q.2. A five digit number is chosen at random, What is the probability that the product of the digits is an even number?
    Q1. 7*7 *4 = 49*4 = 196

    (if no repetition, then 6*5 *4 =30*4 = 120)


    Q2.
    6561*9
    729*7
    81*5
    9*3
    Total=64584

    Total 5digit numbers=90000

    P = 64584/90000 ~ 0.71
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    DMJ
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    Re: three-digit number.

    Q1
    a) with repetition
    7*7*4=196

    b)without repetition
    first two digits -both even 3!/1!=6 times number of odd digits left *4 =24
    first two digits -both odd 4!/2!=12 times number of odd digits left *2 =24
    first two digits -one even one odd 3*4=12 times number of odd digits left *3=36

    asw =84

    Q2.
    in order to have product of any number of numbers even, one of numbers must be even.

    The probability that all five digits are odd (assuming that 0 is even) is:
    (5/10)^5 = (1/2)^5 =1/32 the probability that at least one of digits is even =31/32

    asw 31/32

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    Re: three-digit number.

    Q#1
    1)with repetition
    7 * 7* 4 = 196

    2)without repetition
    a) odd odd odd = 4*3*2 = 24
    b) odd even odd = 4* 3* 3 = 36
    c) even odd odd = 3 * 4* 3 = 36
    d) even even odd = 3* 2* 4= 24
    Total 120

    Q#2
    1- ( probability that all numbers are odd)
    1 - ( (1/2)^5) = 31/32

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    Re: three-digit number.

    yap. second is 31/32
    just learned th method segregation from another thread.
    Opportunities seem Bigger going, than coming.
    make way for th bull -- Thebullfighter.

    Happy New Year 2005 to All.

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    Re: three-digit number.

    Quote Originally Posted by thebullfighter
    Q1.
    (if no repetition, then 6*5 *4 =30*4 = 120)
    Hey bull, how did you get this ?

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    Re: three-digit number.

    Quote Originally Posted by shaq
    Hey bull, how did you get this ?
    u testin' me or u din't actually get it... gotta be kiddin me, i learned P&C & P analysin thy answers & studyin links provided by u..

    Q.1. How many three digit odd numbers can be formed using the digits 1,2,3,4,5,6 and 7?


    odd no.s-- 1,3,5,7

    Case 1-- Last digit is 1 (fixed)

    so other positions can be filled in (7-1=6): 6*5 ways

    similarly for other 3 odd numbers.
    Hence, 6*5 *4=120

    how did i do???
    Opportunities seem Bigger going, than coming.
    make way for th bull -- Thebullfighter.

    Happy New Year 2005 to All.

    AID Appeal for Tsunami Disaster Relief

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    Re: three-digit number.

    Answer for the first question, 7*7*4= 196
    For the second, 1- ( 5/10 )^5 or 1 - (1/2)^5 =

    Hey Bullfighter good job for solving q.1 without repetition.

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    Re: three-digit number.

    Quote Originally Posted by thebullfighter
    u testin' me or u din't actually get it... gotta be kiddin me, i learned P&C & P analysin thy answers & studyin links provided by u..

    Q.1. How many three digit odd numbers can be formed using the digits 1,2,3,4,5,6 and 7?


    odd no.s-- 1,3,5,7

    Case 1-- Last digit is 1 (fixed)

    so other positions can be filled in (7-1=6): 6*5 ways

    similarly for other 3 odd numbers.
    Hence, 6*5 *4=120

    how did i do???
    Good job bull. I split it up differently ( but yours was simpler).
    Kudos to you kid..

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    Re: three-digit number.

    heeey... thanx man. (shaq just praised mine over 'shaq's' own method, tht too for P.. now, this is an honour.)
    Opportunities seem Bigger going, than coming.
    make way for th bull -- Thebullfighter.

    Happy New Year 2005 to All.

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