Latest self Aptitude Question SOLUTION: a forgets telephone no of b. he remembers is no had 8 digits and ended with odd no and had exact one 9.how many possible nos a try to have to be sure he gets correct no??

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(#M40018505) SELF question urgent Keep an EYE

a forgets telephone no of b. he remembers is no had 8 digits and ended with odd no and had exact one 9.how many possible nos a try to have to be sure he gets correct no??

naina (11 years ago)

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Jasmine Khan  (11 years ago)

case 1) 9 is at the end which is odd.
and we have to chose exactly one 9.
so the place of 9 is at the end.
remaining all the 7 digit will contain numbers from 1,2,3,...8
i.e. 8C1*8C1*8C1*8C1*8C1*8C1*8C1*1=8*8*8*8*8*8*8*1
or......
case 2)the number ended with odd number and it is not 9 that means last digit of the number will contain any one of 1,3,5,7 and remaining 7 digit will contain any number from 1,2,3,...8 and 9 will be fitted any one of 7 places.
i.e.7(9C1*8C1*8C1*8C1*8C1*8C1*8C1*4C1)=7*9*8*8*8*8*8*8*4
therefore no of chances will be.
8*8*8*8*8*8*8*1+7*9*8*8*8*8*8*8*4

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devendra  (11 years ago)

1*9*9*9*9*9*9*4
1 for 9 no. which is fixed
9 for any digit can be selected
4 for odd no. excluding 9

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naina  (11 years ago)

ans is 300.9^5

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naina  (11 years ago)

but how xplain pls??

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