SOLUTION: 30 students -26 are right handed, 10 walk to school and 9 of the walkers are right- handed. Find the probability that a student chosen at random; i) is left-handed and walks to s

From this fragment of the condition  ". . . 10 walk to school and 9 of the walkers are right-handed" 

one may conclude that one (and only one) of 10 walking to school is left-handed.


Therefore, the answer to  i)  is  P =  = 0.1 = 10%,   and 

           the answer to  ii) is  P =  = 0.1 = 10%.



Next, since of 30 students 26 are right-handed (given), it means that 4 = 30-26 are left-handed.


Of these 4 left-handed, only one walks to school, as we established ABOVE.

Hence, the rest  4-1 = 3 left-handed do not walk to school, giving answer to iii) :

    P (does not walk to school if we know the student is left-handed) =  =  = 0.1 = 10%.