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?

In a school, the duration of a period in junior section is 45 minutes and senior section is 1 hour. If the first bell for each section rings at 10:00 a.m., when do the two bells ring together again?

The elements Li, Na and K, each having one valence electron, are in period 2, 3 and 4 respectively of modern periodic table. (1) In which group of the periodic table should they be? (ii) Which one of them is least reactive ? (iii) Which one of them has the largest atomic radius? Give reason to justify your answer in each case.

Suppose a company needs a computer for some period of time. The company can either hire a computer for Rs. 2,000 per month or buy one for Rs 25,000. If the company has to use the computer for a long period, the company will pay such a high rent, that buying a computer has to use the computer will be cheaper. Find the number of months beyond which it will be cheaper to buy a computer.

A thin rectangular magnet suspended freely has a period of oscillation equal to T. Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is T' , then the ratio T'/T is

In a scholl students thought of planting trees in and around the school to reduce air pollution. It was decided that the number of tress, 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 with plant I tree, a section of Class II will plant 2 trees and so on till Class XII. Three are three sections of each class. How many tress will be planted by the students ?

Two cars are approaching each other on a straight road and moving with a velocity of 60 kmph. If the sound produced in one car is of frequency 500 Hz, what will be the frequency of sound as heard by a person sitting in another car ? When the car has crossed and moving away from each other , what will be the frequency of sound as heard by the same period ? (speed of sound in air is 332 ms^(-1) )