The principal sanctioned a certain amount of money to the librarian to purchase some mathematics books costing Rs90 each . She could buy 80 books . Then she approached to a publisher who offered her a 20% discount . Find the number of copies of mathematics books which she could buy from the publisher for the sanctioned money.

Juhi wants to buy a bicycle. She goes to the market and finds that the bicycle she likes is available for ₹1800. Juhi has ₹ 600 with her. So, she tells the shopkeeper that she would not be able to buy it. The shopkeeper, after a bit of calculation, makes the following offer. He tells Juhi that she could take the bicycle by making a payment of ₹600 cash down and the remaining money could be made in two monthly instalments of ₹610 each. Juhi has two options one is to go for instalment scheme or to make cash payment by taking loan from a bank which is available at the rale of 10% per annum simple interest. Which option is more economical to her?