1. When decimal currency came to Australia in 1966 (that's exactly 50 years ago!), there were 6 coins -- 1 cent, 2 cent, 5 cent,
10 cent, 20 cent and 50 cent coins. What is the SMALLEST
number of these coins you would need to make 89 cents?

To find the smallest amount of coins needed, we start taking the coins with the biggest value until we get to the desired value.

Doing this, we get that the smallest number of coins is: 6

89 cents:

89 is more than 50 cents, but less than 50*2 = 100, so 1 50 cent coin is needed, which leaves 89 - 50 = 39 cents remaining.39 is more than 20 cents, but less than 20*2 = 40, so 1 20 cent coin is needed, which leaves 39 - 20 = 19 cents remaining.19 is more than 10 cents, but less than 10*2 = 20, so 1 10 cent coin is needed, which leaves 19 - 10 = 9 cents remaining.9 is more than 5 cents, but less than 5*2 = 10, so 1 5 cent coin is needed, which leaves 9 - 5 = 4 cents remaining.The remaining 4 cents are achieved with 2 2 cent coins.

Thus, the smallest amount of coins needed is 1 + 1 + 1 + 1 + 2 = 6.

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