The average of 5 numbers, arranged in a row, is 309. The average of the first two of these numbers is 431 and the average of the last two of these numbers is 231.5. What is the value of the number at the center of the row?

The cost of a new scooter is Rs 25000, at the end of each year its value becomes 80% of the starting price of that year, what will be the cost of the scooter after 3 years?

If xy(x+y)=1, then $$ {1\over x^3 y^3}-{x^3-y^3}$$ is equal to-

30 persons can do a piece of work in 24 days. How many more people are required to complete the work in 20 days?

In ΔABC, ∠C=90° and CD is perpendicular to AB at D. If AD/BD=$$ {\sqrt{k}}$$, then AC/BC=?

A shopkeeper earns a profit of 15% after selling a book at 20% discount on the printed price. The ratio of the cost price and printed price of the book is : 

In a one kilometre race A, B and C are the three participants. A can give B a start of 50m. and Ca start of 69 m. The start, which B can allow C is

If two numbers are each divided by the same divisor, the remainders are respectively 3 and 4. If the sum of the two numbers be divided by the same divisor, the remainder is 2. The divisor is