A school has 8 periods a day each of 45 minutes duration. How long would each period be, if the school has 9 periods a day, assuming the number of school hours to be the same?

A manufacturer has three machines I, II and III installed in his factory. Machines I and II are capable of being operated for at most 12 hours whereas machine III must be operated for at least 5 hours a day. She produces only two items M and N each on the three machines are given in the following table: SHe makes a profit of Rs 600 and Rs 400 on items M and N respectively. How many of each item should she produce so as to maximise her profit assuming that she can sell all the items that she produced? What will be the maximum Profit?

A packet of plain biscuits costs Rs 6 and that of chocolate bisuits costs Rs 9. A house-wife has Rs 72 and wants to buy at least three packets of plain biscuits and at least four of chocolate biscuits. How many of each type should she buy so that she can have maximum number of packets? Make it as a LPP and solve it graphically.

A certain radioactive substance has a half period of 30 days. What is disintegration constant?

In a school, student thought of planting trees in and around the school to reduce air pollution. It was decided that number of trees, that each section of each class will plant, will be the same as the class, in which they are studying, e.g, - a section of Class I will plant 1 tree, a section of Class II will plant 2 trees and so on till Class XII. There are three sections of each class. How many trees will be planted by the students ?