If you were to dial any 7 digits on a telephone in random
order, what is the probability that you will dial your own
phone number?
Assume that your telephone number is 7-digits.
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Answer / guest
1 in 10,000,000
There are 10 digits i.e. 0-9. First digit can be dialed in
10 ways. Second digit can be dialed in 10 ways. Third digit
can be dialed in 10 ways. And so on.....
Thus, 7-digit can be dialed in 10*10*10*10*10*10*10
(=10,000,000) ways. And, you have just one telephone number.
Hence, the possibility that you will dial your own number is
1 in 10,000,000.
Note that 0123456 may not be a valid 7-digit telephone
number. But while dialing in random order, that is one of
the possible 7-digit number which you may dial.
| Is This Answer Correct ? | 35 Yes | 1 No |
Answer / raju
Here is the answer :
Suitable condition are only 1.
Total conditions are 9 X 10 X 10 X 10 X 10 X 10 X 10 = 9000000.
I am taking the first digits as 9 because if phone number is
7 digit is cannot have ZERO at the start. so probablity is :
1 / 9000000
| Is This Answer Correct ? | 9 Yes | 5 No |
Answer / george prasanna
I agree with Raju...
the seven positions are
- - - - - - -
first position (1-9)=9 ways
second position (0-9)=10 waya
third position (0-9)=10 waya
fourth position (0-9)=10 waya
fifth position (0-9)=10 waya
sixth position (0-9)=10 waya
seventh position (0-9)=10 waya
so one in 9x10^6 ways
so probability is 1/9000000
| Is This Answer Correct ? | 7 Yes | 3 No |
Answer / vicky
possible numbers tat can be pressed r 0-9.totally ten.
but,we r going to have our telephone number as a 7digit....
overall probability is 10c7.
but,to select a number from 0 to 9 once,our required
probability is 10c1..we r gonna use it 7 times as they
didn't mention about the repetition of values.
so,the probability of choosing a number is 7times 10c1.
therefore,the answer might be
(7*10c1)/(10c7)
=70/120
=.583333333
| Is This Answer Correct ? | 1 Yes | 6 No |
Answer / roop anand
tot no.of digits in telephone is 10(0-9)
in tat no of digits to be pressed is 7.
so the prob = 7C1/10C7
=7/720
=.01
| Is This Answer Correct ? | 1 Yes | 9 No |
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