Question

Seven digit numbers are made from using all digits, repetition of digits is allowed. Then the probability that the sum of digits of a number is $61,$ is

• A. $\frac{28}{{10}^7}$
• B. $\frac{28}{9\times {10}^6}$
• C. $\frac{{10}^4}{9^6}$
• D. $\frac{9^4}{{10}^7}$

Answer 1

Answer: (B)

$\frac{28}{9\times {10}^6}$

Seven digit numbers made by using all digits $\left(0,1,2,3,4,5,6,7,8,9\right)$ is

$\Rightarrow 9\times 10\times 10\times 10\times 10\times 10\times 10=9\times {10}^6$

Then, probability that the sum of digits of number is 61 $=\frac{28}{9\times {10}^6}$