Probability of selecting a red baloon is 1/6 and probability of not selecting a red baloon = 5/6.
(a). Probability of at least 1 red baloon
= 1/6*5/6*5/6*3 + 1/6*1/6*5/6*3 + 1/6*1/6*1/6
(b) Probability of exactly one red baloon
= 1/6*5/6*5/6*3 = 25/72.
i am getting 1/2 as answer
this is how I did it.
total sample space=6C3=20
red balloon can be selected in only 1 way , the other 2 balloons can be selected 5C2=10
so probability of selecting atleast one red balloon is 10/20=1/2
part B of the question is also the same in my opinion, i think it is just worded differently. since there is only one red balloon . the probability of selecting exactly one red balloon will also be the same i.e 1/2
vivek what is the OA
please also keep posting the OA so that we know whether our calculations are right or not.