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).
What about the compulsory random NZ coin?
ReplyDeleteI could probably get away with swapping one of the 20c coins out for a NZ 20c coin; unless I check closely, I don't notice the difference. so I assume no-one else does either.
ReplyDelete