Lets part from saying that the probability of obtaining any one of these scores is:P=140Since each of these events is mutually exclusive, the probability of obtaining a score less than 40 is:
P(X<40)=P(X=1/30∪1/31∪...∪1/39)=P(1/30)+P(1/31)+...+P(1/39) = 1/40+1/40+...+1/40 =9/40