Question

The table below shows the number of students in each class in a school. The percentage (%) of the students in each class who wear glasses is also shown.

Class	Form 1	Form 2	Form 3	Form 4
Number of students	60	56	44	40
Percentage (%) with glasses	10%	12.5%	25%	17.5

1. A student is chosen at random from the school.
   Determine the:
   1. probability that the student is in form 4. 
   2. probability that the student wears glasses. 
2. Two students are chosen at random from the school.
   Determine the:
   1. probability that one of the two students is in form 1 while the other student is in form 4.   
   2. probability that one of the students is in form I while the other is in form 4 and both wear glasses.

Answer 1

1.  
   
   1. P(F4)= 40  = 0.2
                 200
   2. P(s)=p(F1s or F2s or F3s or F4s)
      = (0.3 x 0.1) + (0.28 x 0.125) + (0.22 x 0.75) + (0.4 x 0.175)
      = 0.265
   3.    
      1. P(F1 &F4) = 2(0.3 x 0.2)
         = 3  or 0.12
           25
      2. P(F1s & F4s OR F4S & F1s)
         = 2(0.3 x 0.1 x 0.2 x 0.175)
         = 0.13

Comments

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