23. a) Show that the number of positive integers less than or equal to $x$ that are divisible by the positive integer $d$ is given by $[x / d]$.
b) Find the number of positive integers not exceeding 1000 that are divisible by 5 , by 25 , by 125 , and by 625 .
c) How many integers between 100 and 1000 are divisible by 7 ? by 49 ?
25. .) $200,40,8,1$ c) 128,18