The simple interest on a sum of money for 10 year is Rs. 3130. If the principal becomes 5 times after 5 years, then what will be the total interest (in Rs) obtained after 10 years? 

The average of 8 readings is 24.3, out of which the average of first two is 18.5 and that of next three is 21.2. If the sixth reading is 3 less than seventh and 8 less than eight, what is the sixth reading? 

A motorboat, whose speed is 45 km./hr. in still water goes 180 km. downstream and comes back in a total of 9 hours. The speed of the stream (in km/hr.) is-

At what rate percent per annum will a sum of Rs.5000 amount to Rs.6000 in 4 years?

There are 45 male and 15 female employees in an office. If the mean salary of the 60 employees is Rs 4800 and the mean salary of the male employees is Rs 5000, then the mean salary of the female employees is

120 men consume 720 kg of rice in 30 days. In how many days can 90 men consume 270 kg?