Quantitative Aptitude - Arithmetic Ability Questions

If ab+ba = -1, then the value of a2b-b2a is

The compound interest earned in two years at 12% per annum is Rs 10176. What is the sum (in Rs) invested?

A canal of a village can be cleaned by 24 villagers in 12 days. The number of days in which 36 villagers can clean the canal is ?

The average age of 80 boys in a class is 15 years. The average age of a group of 15 boys in the class is 16 years and the average age of another 25 boys in the class is 14 years. What is the average age of the remaining boys in the class?

Ramesh sold a book at a loss of 30%. If he had sold it for Rs. 140 more, he would have made a profit of 40%. The cost price of the book is

A fan was sold for Rs. 3600 at a loss of 4%. What would be the gain or loss percent ifit was sold for Rs. 4200?

If the selling price is Rs 2125 after getting a discount of 15% what was the marked price?

If a(a + b + c) = 45, b(a + b + c) = 75 and c(a + b + c) = 105, then what is the value of (a2 + b2 + c2 )?