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Expert: - 10/20/2008


Question
In a large locality, 60 percentage of families have  a car, 50 percentage have an air condition and 30 percentage  have both . find the percentage  of families that have
a.    at least one of the items
b.    neither of the two
c.    have only air conditioner.  

Answer
Draw a square and quarter it with a horizontal line and a vertical line.  

The two squares on top are for those with a car.  Write 60 off to the right.

THe two squares on the left are for those with an air conditioner.  Write 50 below these two.

The top left square is for those having both.  Write a 30 goes in it.

For the two left squares, note that we have 30+(bottom square)=50, so that 20 goes in the bottom square.

On the two top squares, note that we have 30+(right square)=60, so that 30 goes in the right square.

Now we have three squares filled in (30,20, and 30), so to get the value for the last square, take 100-(30+20+30)= ?  Well, 30 plus 20 plus 30 is 80, and 100 minus 80 is 20, so the bottom right square should have a 20 in it.

Basically, to summarize, your squares should look like this:
30 30 | 60
20 20 |
-----
50.

Answers
a. The answer is the sum of the top two squares plus the bottom left square.

b. The answer is the number in the bottom right square (the one that is not on the top or the left).

c. The answer to this one is no car (bottom) and air conditioner (left), so it's the number in the bottom left.

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Scott A Wilson

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