The product of the two numbers is 1500 and their HCF is 10. The number of such possible pairs is/are: 

Vivek and Raja had some books whose ratio was 7: 9 and similarly the ratio of books of Abhishek and Raja was 7: 15, then tell us what was the ratio of books of Vivek and Abhishek?

A cloth merchant sold half of his cloth at 20 % profit, half of the remaining cloth at 20 % loss and the rest was sold at its cost price. In the total transaction, his gain or loss will be 

A vessel contains 20 litres of acid. 4 is taken out of the vessel and replaced by the same quantity of water. Next 4 litres of the mixture are withdrawn, and again the vessel is filled with the same quantity of water. Then find the ratio of acid left in the vessel with the quantity of acid initially in the vessel is:

if the monthly salary of a fan employee is increased by $$ 2{2\over 3}\% $$, he gets 72 rupees more. His Monthly salary (in rupees) is:

There are four numbers in a set. The mean of the three smallest numbers is 9, whereas the mean of the three largest ones is 11. What is the range of the data set? 

A sample of 50 litres of glycerine is found to be adulterated to the extent of 20 % . How much pure glycerine should be added to it so as to bring down the percentage of impurity to 5 %? 

If α and β are the roots of equation x² - 2x + 4 - 0, then what is the equation whose roots are α³/β² and β³/α²?