I'm sure someone has posted this somewhere before, but I've been curious about the number of different coins I need to carry around to ensure I can always reach the exact change for any amount between 5c and $5 (in Australia 5c is the lowest denomination of coin). Tonight I decided to work out a set of coins I would be happy carrying around if minimising the weight of my wallet ever actually becomes important to me. Interestingly, the weight/value ratio of 5 (0.566g/c), 10 (0.565g/c) and 20 (0.565g/c) cent pieces is so similar that it doesn't really matter (on a weight/value basis) which of these is chosen. On the other hand, I also dislike carrying large numbers of coins, so I came up with this combination of coins:
- 2 × $2 (13.2g)
- $1 (9g)
- 50c (15.55g)
- 2 × 20c (22.6g)
- 10c (5.65g)
- 5c (2.83g)
This gives a total of 8 coins, adding up to $6.05 and weighing 68.83g total. Replacing a $2 coin with a $1 coin will give you the same flexibility while carrying around one dollar less, but you'll also be carrying 2.4g more (according to the
source of all knowledge).
