QR probability either or %

[glme]

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When there is a question like: 60% does A, 30% does B, and 15% does both. what is the % of people doing only either A or B?


I see that sometimes you subtract 15% from both of the population and add: (60-15)+(30-15)
But other times you just subtract once from the total: 90-15


Could someone please help me with distinguishing the two?


Thank you very much for your help!!

 

[nattmelson]

Construct a Venn diagram

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[DAT Destroyer]

When there is a question like: 60% does A, 30% does B, and 15% does both. what is the % of people doing only either A or B?


I see that sometimes you subtract 15% from both of the population and add: (60-15)+(30-15)
But other times you just subtract once from the total: 90-15


Could someone please help me with distinguishing the two?


Thank you very much for your help!!

It all depends on the way the question is worded. Set up the problem the following way:
If 60% does A and 30% does B and 15% does both then 60-15=45% does only A and 30-15=15% does only B.
If the question states what percentage does A or B then the answer is: 45+15+15=75% or 60+30-15=75%>
If the question states what percentage does A or B but not both, the answer is
45+15=60%

You can also draw a Venn diagram to figure out the answer