howmany 4 digit numbers exist,such that sum of digits is equal to 7.
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0
Answer:Answer to this question is 84
Explanation:
Answered by
1
Answer:
Explanation:
- As the sum of digits is 7 so it is the question of permutation and combination to distribute n identical item to r persons
so let a+b+c+d=7
so (7+4-1)C3
but a can't be zero as it is a four digit number so b+c+d can't be 7
(7+4-1)C3 - (7+3-1)C2
120-36=84
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