zooki wrote: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 must be a prime number. How many student identification numbers can be created?
[source: Veritas free practice test for GMAT]
Please find the below solution.
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1) Given that 1st number not equal to zero
2) last number should be a prime number
Solution
Out of 9 numbers, we need to select 1 ----> 9C1
Out of 10 numbers including zero , we need to select one ----> 10C1
Out of 10 numbers including zero , we need to select one ----> 10C1
Last digit Out of 4 prime numbers, we need to select one ----> 4C1
Total ---> 9c1*10c1*10c1*4C1
----> 3600 ways of creating a 4 digit identification number
