Product of digits of a 2-digit number is 27. If we add  54 to the number, the new number obtained is a number formed by interchange of the digits. Find the number.

Sum of two numbers is thrice their difference. Their ratio is 

The difference between the sum of four consecutive odd numbers and three consecutives even numbers together is 20. Also, the largest even number is 5 more than the largest odd number. What is the sum of the smallest odd number and the smallest even number?

Find the average of all prime numbers from 1 to 20?

Find the value of $$ {1\over{2×5}}+{1\over {5×8}}+{1\over {8 × 11}}+......{1\over {23 × 26}}=?$$

What least value which should be added to 1812 to make it divisible 7,11 and 14? 

If the arithmetic means of 3a and 4b is greater than 50, and a is twice b, then the smallest possible integer value of a is: 

The difference of a number consisting of two digits from the number formed by inter changing the digits is always divisible by: