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why do we do 32 raise to 3 ?
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why do we do 32 raise to 3 ?


Hi

There are 3 places to be filled up, and each place can be filled up with any of the 32 possible alphanumeric values.
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chetan2u KarishmaB I didn't understand the explanation of question 3rd at all. Could you please help explaining it again?
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chetan2u KarishmaB I didn't understand the explanation of question 3rd at all. Could you please help explaining it again?


The 14 alpha numerical code is ABCDEFGHIJKLMN
The first four ABCD are randomly generated.
8 to 13 are timings of purchase and the 14 is the unit digit of all numerical values.

We are concerned with 5, 6 and 7 place.
These are taken from the mail and could be a digit or an alphabet.
Proposal 1 does not put any restriction but proposal omits FOUR alphabets, so we can have anything other than these 4 alphabets.
Thus, (26-4)+10 or 32 values.
Each of 5th, 6th and 7th places can take any of the possible 32 values=> 32*32*32
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­1. Suppose that Proposal 2 has been adopted and that a customer has been issued a CID of 1039str0129016. For each of the following statements about this customer, select Could be true if, in light of the given information, the statement could be true. Otherwise, select Could not be true.

- 4 random numbers: 1039
- First 3 alphanumber allowablecharacters of email str
- hhmmss of the 1st purchase: 01:29:01
- Checking digit: 6

The customer's email was str@example.com. => Could not be true
str must be reversely transformed to another 3 characters

The customer began shopping at 10:39 in the evening on the day before the first purchase. => Could be true
The customer could start shopping at 10:39 p.m and ended up making the first purchase after a few hours, which is 1:29 a.m of the following day


The customer's first purchase was made 16 seconds after 1:29:00 in the morning. => Could not be true
The first purchase is made at 1:29:01, not 1:29:16


2. For each of the following principles named in the Customer Identifiers tab, select Explicitly mentioned in Proposal I if that principle is explicitly mentioned in the description of Proposal 1. Otherwise, select Not explicitly mentioned in Proposal 1.

Database Constraints => Explicitly
Only containing characters from the allowed table

Error Checking => Not Explicitly
This is only available in Proposal 2 (checking digit)

Meaningful => Explicitly
Having info of part of the email address and the time of 1st purchase


3. How many 3-character alphanumeric sequences can appear as the 5th, 6th, and 7th characters of a valid CID under Proposal 2? [32,768]

5th, 6th and 7th characters are those alphanumeric allowable characters (taken from the email address)

For Proposal 1: There are 36 (=6*6) allowable characters 

For Proposal 2: There are only 32 left (= 36 - 4 letters a i o u which all become e)

Number of valid sequences: 32 * 32 * 32 

- Method 1: Use the calculator
- Method 2:
  + Answer ends with 8 (=2*2*2)
  + Answer > 30 * 30 * 30 = 27,000
  ==> The only which fits is 32,768
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3rd question solution.

We have 26 alphabets and digits that we can use to fill in the 5th, 6th, and 7th spaces in the CID, therefore we have 36 characters to choose from for each of the 3 spaces (repetitions allowed)

Normally, this would mean that we have 36^3 combinations but Proposal 2 has a restriction under which we can't use 4 letters and instead we have to use the letter 'e' in place of that, this reduces our characters to 32 but the formula remains the same.

We have 32 * 32 * 32 combinations. You could use the calculator here but it is quicker to estimate, 2^5 * 2^5 * 32= 2^10 * 32, 2^10 is 1024, so the answer should be 32 thousand something.
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How did it began shopping at 10:39 if the numbers are randomly generated? Bunuel KarishmaB
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The time they begin shopping is a trap in this instance as it isn't relevant for the CID, the time they made their first purchase is relevant however. As long as those two pieces of information do not conflict, the first doesn't matter. The fact that the time they started shopping and the randomly generated digits are the same is a coincidence meant to confuse you.
KK12333
How did it began shopping at 10:39 if the numbers are randomly generated? Bunuel KarishmaB
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chetan2u



Hi

There are 3 places to be filled up, and each place can be filled up with any of the 32 possible alphanumeric values.
hi chetanu2u, I a not able to understand as in proposal 1 it is explicitly mentioned that timestamp would there after 3 alphabets in cid after it timestamp will be followed but in proposal 2 it is saying that it is an extension of proposal 1 and character will be transformed according to the table but in that too 5,6 and 7 place are filled by numbers so how can we say that these places can be filled with alphabets shouldn't it be filled with numbers only from 0-9....Kindly help me with this....
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SukhAgam

hi chetanu2u, I a not able to understand as in proposal 1 it is explicitly mentioned that timestamp would there after 3 alphabets in cid after it timestamp will be followed but in proposal 2 it is saying that it is an extension of proposal 1 and character will be transformed according to the table but in that too 5,6 and 7 place are filled by numbers so how can we say that these places can be filled with alphabets shouldn't it be filled with numbers only from 0-9....Kindly help me with this....
The 5th, 6th, and 7th characters come from the first three characters of the customer’s email in Proposal 1, not from the timestamp. Since they’re from the email, they can be letters or digits, not just numbers.
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i still doesn't understand this part, can you please explain me again and if possible in detail with the proposal set mentioned in the question stem
cheshire
The time they begin shopping is a trap in this instance as it isn't relevant for the CID, the time they made their first purchase is relevant however. As long as those two pieces of information do not conflict, the first doesn't matter. The fact that the time they started shopping and the randomly generated digits are the same is a coincidence meant to confuse you.

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The time they begin shopping is a trap in this instance as it isn't relevant for the CID, the time they made their first purchase is relevant however. As long as those two pieces of information do not conflict, the first doesn't matter. The fact that the time they started shopping and the randomly generated digits are the same is a coincidence meant to confuse you.


In CID 1039str0129016:

• 1039 are random digits with no link to time, date, or any customer detail.

• str012901 comes from Proposal 1 after applying the transformation table to str. 012901 represents the timestamp of the first purchase at 1:29:01 AM.

• 6 is the check digit. To find it, add all numeric digits before it: 1 + 0 + 3 + 9 + 0 + 1 + 2 + 9 + 0 + 1 = 26, and the units digit of 26 is 6, which becomes the check digit.
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