Questions
The number of rational numbers lying in the interval (2015, 2016) all whose digits after the decimal point are non-zero and are in decreasing order is
detailed solution
Correct option is C
A rational number of the desired category is of the form 2015. x1x2…xk and 9 ≥ x1 > x2 > … > xk ≥ 1. We can choose k digits out 9 in 9Ckways and arrange them in de creasing order in just one way. Thus, the desired number of rational numbers is 9C1+9C2+…+ 9C9=29−1Similar Questions
is equal to
799 666 8865
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