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29 Feb 2016, 10:51
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B
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Difficulty:
5%
(low)
Question Stats:
89% (01:07) correct
11%
(02:00)
wrong
based on 232
sessions
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Each student at a certain business school is assigned a 4-digit student identification number. The first digit of the identification number cannot be zero, and the last digit of the identification number must be prime. How many different student identification numbers can the school create?
A. 9,000
B. 3,600
C. 2,700
D. 2,592
E. 1,944
A. 9,000
B. 3,600
C. 2,700
D. 2,592
E. 1,944
29 Feb 2016, 20:23
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Bunuel
Hi,
these are simple Combinations problems..
But the most important point here is to reread if the combination is of different digits or the same digit can be repeated..
Here, there is no restriction..
Let the number be ABCD..
1) A can be any of the 10 digits, 0-9, except 0, so 9 ways..
2) B and C can be any of the 10 digits, so 10 ways each..
3) D is a prime number, so 2,3,5,7 fit in--- 4 ways..
Total ways= 9*10*10*4=3600
B
Updated on: 03 Mar 2016, 03:08
Originally posted by TeamGMATIFY on 03 Mar 2016, 02:27.
Last edited by TeamGMATIFY on 03 Mar 2016, 03:08, edited 1 time in total.
Last edited by TeamGMATIFY on 03 Mar 2016, 03:08, edited 1 time in total.
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Bunuel
The identification number is of the form _ _ _ _
1. First digit cannot be 0
2. Middle digits can be anything
3. Last digit has to be prime - 2, 3, 5, 7
We can have the following number of possibilities for each space
__ __ __ __
9 10 10 4
Total cases = 3600
Option B
