List of top Logical Reasoning Questions on Number Systems

The digits of the number 2365643879 are arranged in ascending order from left to right. What is the difference between the two digits where one digit is 3rd from the right and the other digit is 4th from the left?
How many 4-digit positive integers divisible by 3 can be formed using only the digits {1, 3, 4, 6, 7}, such that no digit appears more than once in a number?
The sum of the following infinite series is
$2+ \frac{1}2 + \frac{1}3 + \frac{1}4 + \frac{1}8 + \frac{1}9 + \frac{1}{16} + \frac{1}{27}+ .....$