 Hello and welcome to the session. In this session we will discuss use of percentages. Let's first learn how we interpret percentages. Like for example, you have a statement which says that 30% of the total people in a party are men. Now here by 30% we mean 30 parts out of 100 and we write it as 30 upon 100. So we say that out of 100 people 30 are men. So this is how we interpret percentages. Next we discuss converting percentages to how many. We have that 10% students of a class of 50 like eating apples. We need to find out how many students like eating apples. This can be done in two ways. One we have that out of 100, 10 students like eating apples. Since we have the 10th person students like eating apples. So we say that out of 100, 10 students like eating apples. Now we need to find out that out of 50 students, students who like eating apples is given by 10 upon 100 into 50. And this is equal to 5. So we say that out of 50 students, 5 students like eating. Now the other way of doing this is that we find out 10% of the total number of students that is 50. And so this is equal to 10 upon 100 into 50 which comes out to be equal to 5. So we say that 5 students like eating apples. Next we have ratios to persons. Sometimes we are given parts in the form of ratios and we need to convert them to percentages. Let's see how we do this. Consider this figure in this. We need to find the percentage of the figure shaded red. Now as you can see we have three colors in this figure. Green, yellow and red. Now the ratio of green is to yellow is to red is given as. 2 is to 2 is to 1 since we have two parts in this figure are shaded as green. Two parts are shaded as yellow and one part is shaded as red. Now 2 plus 2 plus 1 equal to 5. This is the total of all parts. So the percentage of the figure shaded as red is equal to 1 since we have just one part is shaded as red upon the total parts of the figure that is 5 into 100% which is equal to 100 upon 5 and this is equal to 20%. So the percentage of this figure shaded as red is 20%. Next we discuss increase or decrease as percent. Sometimes we need to know the increase or decrease in a certain quantity as percentage. Let's see how we do this. We have percentage increase or percentage decrease is equal to the amount of change upon the original amount or base into 100. This is the formula that we use for finding the percentage increase or percentage decrease. Like suppose the population of a city in the year 1997 is equal to 27000. In the year 2000 the population of that city is given as 27,270. Now as you can see obviously there is increase in the population of the city from the year 1997 to the year 2000. So we have percentage increase is given by the amount of change which is given as 27,270 minus 27000 upon the original amount which is 27000 into 100 and this comes out to be equal to 1. So we say that the population of a city increased by 1%. So this completes the session. Hope you have understood the concept of percentages.