$A$ child's game has $8$ triangles of which $3$ are blue and the rest are red,and $10$ squares of which $6$ are blue and the rest are red. One piece is lost at random. Find the probability that it is a
$(i)$ triangle
$(ii)$ square
$(iii)$ square of blue colour
$(iv)$ triangle of red colour

(N/A) Total number of pieces $= 8 \text{ triangles} + 10 \text{ squares} = 18$.
$(i)$ Probability that the lost piece is a triangle $= \frac{8}{18} = \frac{4}{9}$.
$(ii)$ Probability that the lost piece is a square $= \frac{10}{18} = \frac{5}{9}$.
$(iii)$ Number of blue squares $= 6$. Probability that the lost piece is a blue square $= \frac{6}{18} = \frac{1}{3}$.
$(iv)$ Number of red triangles $= 8 - 3 = 5$. Probability that the lost piece is a red triangle $= \frac{5}{18}$.