A box contains 280 coins of one rupee, 50-paise and 25-paise. The value of each kind of the coins are in the ratio of 8 : 4 : 3. Then the number of 50-paise coins is 

The ratio of the ages of two persons is 4 : 7 and the age of one of them is greater than that of the other by 30 years. The sum of their ages ( in years ) is 

In a certain school, the ratio of boys to girls is 7 : 5. If there are 2400 students in the school, then how many girls are there?

A man saves 20% of his  monthly salary. If an account of dearness of things he is to increase his monthly expenses by 20%, he is only able to save Rs. 200 per month. What is his monthly salary?

If 12 men can do a piece of work in 24 days, then in how many days can 18 men do the same work?

A and B together can plough a field in 10 hours but by himself A requires 15 hours. How long would B take to plough the same field?

The average age of students in a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ratio of the number of boys to the number of girls in the class is:

If 10 men or 20 women or 40 children can do a piece of work in 7 days, then 5 men, 5 women and 5 children together can do half of the work in