Step 1:  Find the total number of coins in a kiddy bank

              No. of 50p coins = 100

                No. of  rs 1 coins = 50

                No. of  rs 2 coins = 20

                No. of  rs 5 coins = 10

              Total no. of coins = 100 + 50 + 20 + 10 = 180

          Therefore, total number of possible outcomes = total number of coins = 180

Step 2: Determine the probability of getting a 50 p coin

            NOTE: Let E be the event that 50 p coin falls out.

          Number of outcomes favorable to event E = Total number of 50p coins =100

                P(E) = \frac{\text{Number of outcomes favorable to event E}}{\text{Total number of possible outcomes}} 

                        = \frac{100}{180}

                       = \frac{5}{9}

              Hence,  probability of getting a 50 p coin = \frac{5}{9}

Step 3: Determine the probability of not getting a 5 rupee coin

            NOTE: Let F be the event that the coin falls out is not Rs 5.

              Number of possible outcomes favorable to event F = Total number of coins except Rs 5 coins =180 - 10 =170

                 P(E) = \frac{\text{Number of outcomes favorable to event E}}{\text{Total number of possible outcomes}}

                        = \frac{170}{180}

                        = \frac{17}{18}

          Hence,  probability of not getting a 5 rupee coin  = \frac{17}{18}