Question 1031304: How many 4 digit numbers can be formed out of the digits (3,4,5,6,7)which are greater than 5000 and no digit is repeated.the options are
a)72(correct)
b)27
c)70
d)none of these
I tried to solve it in the following way
if it is a 4 digit number greater than 5000 then the first number can be 5,6 or 7 so we have three choices
the second digit can be any of the above numbers(3,4,5,6,7)so we have 5 choices as no digit can be repeated we are left with 4 and 3 choices for the 3rd and 4th digit respectively
we can summarize it with the help of the fundamental principle of counting as
3*5*4*3=180
but this is wrong,
the correct answer is 72
please reply as soon as possible
thank you
yours sincerely
sukhdeep
Answer by ikleyn(52878)   (Show Source):
You can put this solution on YOUR website! .
1. Any of three numbers (5, 6, 7) in the first (from the left) position;
2. any of 4 remaining numbers in the second position;
3. any of 3 remaining numbers in the third position;
4. any of 2 remaining numbers in the fourth position.
3*4*3*2 = 72.
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