Let's use this question to discuss on drawing and using cumulative frequency curve.
(Click on image to enlarge)
(a) Drawing of cumulative freq curve
(Click on image to enlarge)
Step by step solutions:
Notes:
140 pupils weigh 72.5 kg or less. So if you are interested to find out the number of pupils who weigh more than 72.5 kg. It will be 280 (total number of pupils) - 140 = 140 pupils.
Special attention to (iii) no. of students who weigh more than 65kg. By going UP & ACROSS, we get 20 students. This only means 20 students weigh 65 kg or less. So the rest (280 - 20 = 260) will weigh more than 65 kg
In my next post, I will be discussing the features of box and whisker plot.
Ai Ling Ong
Hi, I'm Ai Ling Ong. I enjoy coaching students who have challenges with understanding and scoring in 'O' Level A-Maths and E-Maths. I develop Math strategies, sometimes ridiculous ideas to help students in understanding abstract concepts the fast and memorable way. I write this blog to share with you the stuff I teach in my class, the common mistakes my students made, the 'way' to think, analyze... If you have found this blog post useful, please share it with your friends. I will really appreciate it! :)
In case, you didn't know, drawing of cumulative Freq curve is out of syllabus.
We do teach them in school as knowledge but students are not required to know how to draw the c.f.curve.
Therefore, Qns like those in (a) will not come out.
They do have to know how to read and interpret it though.
so a more likely Qn would be one where the c.f.curve is given and students are to answer Qn as in (b).
phasis. I was a math teacher in India. Your method is easy to understand. Thank you again.
Informative!