 second lesson of JSE Mathematics in a series of two lessons the topic of this lesson is line graphs the objectives of this lesson are to calculate profit calculate percentage profit draw a line graph from given data let's switch over to hear what Jason and his family are doing hey Jason so tell me how you guys doing with the touch of at school making any profit yet it's going well dad and sure we're making a profit are you sure it's not a lost now tell us don't keep us in agony yeah okay mom but just a minute I'll quickly go fetch my stuff in my room okay okay let me show you I made a line graph for the stock board each week and for how much the stock was bought each week then for each week I calculated the percentage profit that we made we actually have a competition going each month the group that sells the most each month gets a small price oh whoa whoa whoa whoa hold it there I mean you're going a little bit too fast for me one thing at a time please now you were saying something about the line graph yeah sorry I forgot you're a bit old okay I'll show you from the beginning now look in the first week we bought stock for $1,500 the cost price of the stock that we sold was $1,500 the selling price of the stock that we sold was $2,200 well so that means you worked out the profit by calculating the selling price from minus the cost price yeah and that is $2,200 million minus $1,500 which gives us $700 for the first week you're right you're not as old as I thought after all hey I'm warning you Jason sorry mom so you do this exercise every week yes dad but first we need to do stock control to see what we really have left and how do you do that yeah you simply go into the touch up and count the stock then we work out each items selling price according to the cost that sounds like a lot of work yes dad it is but if you really want to be successful in your business you can't afford to slip up yeah so once you have all the information what do you do then we decided to draw a line graph once every four weeks so once every four weeks we put the information onto a line graph now look the bottom line of the line graph shows the cost price and the top line shows the selling price yeah yeah yeah yeah but how do you draw the graph line no line draft yeah yeah let me show you here is the data for the first four weeks of the year on a piece of graph paper I draw an X and Y axis like this and the X axis represents the number of weeks and the Y axis represents the amount of money in the million dollars then I label my accesses and number them now because I work with big amounts I can number my Y axis so that one centimeter equals two hundred dollars you see that hmm I only need four numbers on the X axis so two centimeters on the X axis can represent one week no this is getting just too much for me I need a cup of tea about you guys yeah yeah yeah that would be fine can I have some juice please mom yes yeah thank you mom Jason I did not want to mention this while your mom was around but you were talking about axis and stuff like that it's really not that difficult that yeah accesses are the vertical and horizontal lines on a graph that you must draw before you can draw any graph okay and the whole time I'm thinking we're talking about actual axis chopping wood and stuff like that you know oh dad no not really mom thanks for the juice mom so what's next now we must take the data that I showed you and plot them well you see the data that I showed you we take it and plot them how did now you know as soon as I think I've got it then it just completely lose me what are you talking about the plot and stuff plot simply means that you make a dot on the graph at the right place now how do we know where the correct place is okay I'll show you mom can you give me the figure of the cost price for the first week yeah yeah eat 1500 new bin dollars yes now you take your pencil and your ruler find the amount 1500 on the y-axis and put your ruler in a horizontal direction so that it goes through 1500 now go to your x-axis find week one move vertically up until you reach the ruler and whether to meet you plot a point of the pencil I didn't see what okay I'll do another one okay dad what is the cost price in week two well let's see yeah it's one thousand three hundred and fifty nine million dollars okay mom now look where I'm going to put the ruler on one thousand three hundred and fifty of the y-axis can you see that now this is the amount for week two the weeks are on the x-axis so you must look at the x-axis can you point to the pencil where it should be now move up until you touch the ruler that's right make a dot with a pencil you've got it wow that wasn't too hard now we will complete the plotting of the point for the other two weeks I'll quickly do that and then we draw the line okay but the selling price will do exactly the same because we made a profit each week the line is going to be higher than the line for the cost price yeah to make a difference between the two we'll make it two different colors as soon as our lines meet and the selling price goes below the cost price we know that we are not making a profit any longer now Jason tell me how did you calculate the percentage profit in the table and why did you calculate it okay let me first answer the question why remember that I told you that we have a competition running each month yeah well it is more fair to give the price to the group that makes the highest percentage profit but why is that Jason well sometimes there is less talk in the touch up so the group cannot sell a lot that week yeah when there is more stock the choices are more so they can sell more yeah yeah yeah yes it's all making sense but but I just just just want you to show us how to calculate the percentage profit yes okay look at the selling price and cost price again yeah how do we find the amount of profit that we made I think it is the difference between the two that is selling price minus cost price yeah that's right so during week one it was two thousand two hundred Namibian dollars minus one thousand five hundred Namibian dollars and that is equal to seven hundred Namibian dollars so the amount of profit was seven hundred Namibian dollars so the profit the amount of profit that is that we made is seven hundred Namibian dollars to find a percentage profit we calculate seven hundred Namibian dollars divided by the cost price which is one thousand five hundred yeah and then you multiply it by one hundred and that is equal to forty six point seven percent Wow Jason you have inspired me so much I think I'm going to start my own business like baking biscuits and sell them then I can make money every week hey now that's a brilliant idea you know what you can actually save up and buy that the microwave you always wanted yeah mom but you sure have to bake a lot of biscuits yes I will get right to it but you will have to help me with all the calculations and graphs in the beginning yes your mom if I can have five percent of the profit now you're pushing your luck but okay we can talk about it later but you have to first promise me that you will help me I promise mom let me just get this kitchen thanks mom let's now recap what we've learned today profit is equal to selling price minus cost price excess are vertical and horizontal lines on a graph percentage profit is profit divided by the cost price multiplied by a hundred this brings us to the end of today's lesson goodbye