SOLUTION: In a survey of 400 students in a secondary school,200 were listed as smokers and 300 are listed as gum chewers.150 were listed as both smokers and gum chewers. Find how many studen

Algebra ->  sets and operations -> SOLUTION: In a survey of 400 students in a secondary school,200 were listed as smokers and 300 are listed as gum chewers.150 were listed as both smokers and gum chewers. Find how many studen      Log On


   

Question 1181543: In a survey of 400 students in a secondary school,200 were listed as smokers and 300 are listed as gum chewers.150 were listed as both smokers and gum chewers. Find how many students are either smokers or gum chewers. Illustrate this Venn diagram
Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
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The problem asks to find the number of students in the union of two sets.


This number is equal to  200 + 300 - 150 = 350.    ANSWER


We add the numbers of students in the sets separately and then subract the number of the students in the intersection.


This way to count is called "inclusion-exclusion principle".

Solved and explained.

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To see many other similar  (and different)  problems,  look into my lesson
    - Counting elements in sub-sets of a given finite set
in this site.


Then you will be prepared to solve problems like this one in your post.