Question:
The number of seven digit integers with sum of the digits equal to 10 and formed by using the digits 1,2 and 3 only is
Correct Option: 1
Solution:
CASE-I: $1,1,1,1,1,2,3$
$\mathrm{WAYS}=\frac{7 !}{5 !}=42$
CASE-II: $1,1,1,1,2,2,2$
WAYS $=\frac{7 !}{4 ! \cdot 3 !}=35$
TOTAL WAYS $=42+35=77$
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