Solution:
A rational number of the desired category is of the form 2015. and We can choose k digits out 9 in
ways and arrange them in de creasing order in just one way. Thus, the desired number of rational numbers is
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
A rational number of the desired category is of the form 2015. and We can choose k digits out 9 in
ways and arrange them in de creasing order in just one way. Thus, the desired number of rational numbers is