Here, total marbles = 10 + 20 + 30 = 60 We have to draw 5 marbles out of 60 marbles in $\,{}^{60}C_5$ ways. (i) There are 20 blue marbles. We have to draw 5 marbles out of 20 blue marbles in $\,{}^{20}C_5$ ways. Thus, the probability that all will be blue = $\frac{\,{}^{20}C_5}{\,{}^{60}C_5}$ (ii) There are 10 red marbles and 20 blue marbles. We have to draw 5 marbles out of 30 marbles in $\,{}^{30}C_5$ ways Thus, the probability that atleast one will be green = 1 − $\frac{\,{}^{30}C_5}{\,{}^{60}C_5}$