Quantitative Aptitude - Arithmetic Ability Questions

If a + b = 9 and a2+ b2= 61, then ab is

In a class of 50 students there are 22 girls who scored an average of 35 marks in the test. What is the average marks of the boys if the class average is 42 marks?

To travel 612 km, an Express train takes 9 hours more than Rajdhani. If the speed of the Express train is doubled, it takes 3 hours less than Rajdhani. The speed (in km/hr) of Rajdhani is

The difference between the selling prices of an article sold at 4% and 3% profits is Rs.3 The cost price of the article is :

What will be the acute angle between the hour-hand and the minute -hand at 2:13 p.m?

18 buckets of water fill a tank when the capacity of each bucket is 8 litres. How many buckets will be needed to fill the same tank, if the capacity of the bucket is 12 litres?

A sum of money was invested at the rate of 7.5% S.I. per annum for 4 years. If the investment was for 5 years, the interest earned would have been Rs. 375 more. What was the initial sum invested?

A and B together can complete a task in 12 days. However, if A works alone, completes half the job and leaves and then B works alone and competes the rest of the work, it takes 25 days in all to complete the work. If B is more efficient than A, how many days would it have taken B to do the work by herself?