+0  
 
+1
46
1
avatar+75 

Randomly place +" or -" into the following boxes,

◻ 1/2 ◻ 1/3 ◻ 1/4 ◻ 1/15

What is the probability that the result is positive but no greater than 1/20?

 Jun 24, 2022
 #1
avatar+124509 
+2

 

Getting a common  denominator we have

 

30/60      20/60       15/60     4/60

 

We need the result to be  < 3/60  (but positive)

 

We have 8 possibilities

 + + +           reject  as too large

+ + -            reject  as too large

+ - -             reject as too large

 - -  -              reject  (negative result)

- - +               reject  (negative result)

- + +              reject as too large

+ - +            reject as too large

- + -              reject as too large

 

The probability is  0

 

 

cool cool cool

 Jun 24, 2022

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