Probability problems like fractions
Many probability problems on the test can be solved using simple fractions. Suppose a store owner noticed that if 10 people visit the store, 4 will buy something. If 40 people visit the store, how many will buy, given that assumption?
You can set up a fraction, based on the 4 and 10 as follows.
4⁄10 = people who buy⁄all visitors
So...create a variable (x)...the unknown...that represents the number of people who buy.
Then set up an equation as follows..
4⁄10 = x⁄40
Cross multiply and divide...
4 times 40 = 10 times x
160 = 10x .... Now divide both sides by 10..
16 = x ... so 16 people will buy something if 40 people visit
You could also simply solve the fraction 4⁄10 = 40%
So, 40% of people who visit buy something. So, take 40% of 40 = 16 people ... Same answer ...may be a little faster to solve, also.
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