The sum of three consecutive numbers is 87. The middle number is : 

In a two - digit number, the digit at the unit's place is 1 less than twice the digit at the ten's place. If the digits at units and ten's place are interchanged, the difference between the new and the original number is less than the original number by 20. The original number is: 

Divide 50 into two parts so that the sum of their reciprocals is   $${1\over 12} $$

In a class, there are ' z ' students. Out of them ‘x’ are boys. What part of the class is composed of girls? 

The numerator of a fraction is 4 less than its denominator. If the numerator is decreased by 2 and the denominator is increased by 1, the denominator becomes eight times the numerator. Find the fraction? 

A rational number between $${3\over4} $$ and $${3\over8} $$ is :

If * means adding 6 times the second number to the first number then ( 1 * 2 ) *   3 equals : 

How many even three-digit numbers can be formed from the digits 1 , 2 , 5 , 6 and 9 without repeating any of the digits?