A shopkeeper bought 80 kg of rice at a discount of 10%. Besides 1 kg rice was offered free to him on the purchase of every 20 kg rice. If he sells the rice at the marked price, his profit percentage will be:
A person invested Rs. 2,000 on simple interest for 7 years to obtain a total amount of Rs. 3,400 on a certain annual rate of interest. What was the rate of interest to obtain the above amount ?
Three men do as much work as 4 boys do and the 4 boys can together complete work in 21 days. In how many days will 9 men and 2 boys complete the same work?