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#JambQuestion
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How many four digits numbers greater than 5000 can be formed using the digits 1,2,5,6 and 7 if no digit can be repeated?

A. 420
B. 210
C. 72
D. 24
E. 12

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Solution


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Any four digits number starting with 5, 6 or 7 with the combination of the other numbers will be greater than 5000.

So, in the four digits number, the first digit can be formed by using 5,6 or 7 that is:


First digit can be formed in 3ways




The second digit can be forrmed using any of the remaining four numbers, that is:


Second digit can be formed in 4ways,



likewise;


Third digit can be formed in 3ways,



likewise;


Fourth digit can be formed in 2ways.




Therefore, the four digits number can be formed in
3 × 4 × 3 × 2 =
72 ways




The correct option is C. 72



Source: http://samimath.com/q-permutation-combination-2/

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