I thought I’d tell you a little more about the currencies in Cambodia and why it gets so confusing. The main reason for this is because I can’t do maths. Well, I can, just not quickly in my head and not when trying to work out what you can pay in which denomination. It often feels like I’m in an Edexcel GCSE maths exam. I have written a mathematical challenge for you to have a go at. The answers (that are probably wrong because I’m rubbish ) can be found at the bottom.

*Thomas lives in Cambodia. In Cambodia, they use both the American dollar and the Cambodian Riel. One dollar equals four thousand riel. In Thomas’ wallet, he has twelve one-hundred-riel notes, seven five-hundred-riel notes, one twenty-thousand-riel note, seven one dollar notes, a twenty-dollar note and five receipts he’s keeping because it has the cafes’ WiFi passwords on.*

*a) How much money does Thomas have in dollars (rounding to two decimal places)?*

*Thomas goes to Angkor Mart and buys two bottles of Pepsi twist, for 50 cents each, a loaf of bread for $2.25 and a bottle of water for $0.90. *

*b) Using the fewest notes, what notes could Thomas use to pay the exact amount?*

*Please show your working.*

*c) Instead of paying in the exact amount, Thomas panics and hands over the twenty-dollar note. Thomas receives the change in one-hundred-riel notes. How many one-hundred-riel notes does Thomas now have?*

*Please show your working.*

*d) What is the WiFi password for Joma in Tuol Tompong?*

This is made even more complicated when some companies impose a $1=R4100 exchange rate, in order to prevent any losses. As it’s so confusing, I tend to ignore the small riel notes until days like Saturday, when I had 21 of them in my wallet. So I paid for an iced tea in only 100 and 500 riel notes. I did apologise and avoid eye contact with the cashier as she checked my maths (which I had got wrong- but it was one of those places with the bizarre exchange rate).

Another thing that results in confusion is that the 1000 riel note and 10000 riel note look very similar. One very happy tuk tuk driver thought he had got a pretty good Pchum Ben tip. Instead, I was just tired and gave him $5.25 instead of $3 due to mistaking two notes in my wallet. It’s only until I went to pay with the 10000 riel note later that I realised why he looked so pleased.

Obviously, it’s even more confusing (and slightly depressing thanks to Brexit) when I try to work out how many pounds sterling I have been spending. This perhaps goes to explain why budgeting isn’t my strong point.

ANSWERS: a) $33.18 (if you go by the whole “round up if the next digit is 5 or higher”, but I can’t make money from nowhere, so in the real world it’s $33.17. But where has my 0.5c gone?) b) Four one-dollar notes, one five-hundred-riel note, and one one-hundred-riel note. c) 646 one-hundred-riel notes (don’t forget to add the change given to the twelve notes I already had!) d) They’ve introduced a daily rolling password. It used to be *bananabread9*.