This is not an article; it’s a challenge. A challenge for the Excel community to demonstrate and teach creative thinking using Excel. Nothing is being left out here—so buckle up.
The Inspiration:
This challenge is based on a problem originally posed by Oz du Soleil in one of his videos from December 2019, where three siblings agreed to share the costs of family gifts, each in different proportions. In Oz’s challenge, the goal was to determine how much each sibling owed or was owed.
For our challenge, we’re scaling this up, and it gets a lot more complex.
The Setup:
Instead of three siblings, we’re bringing in six friends: Monica, Chandler, Rachel, Ross, Phoebe, and Joey (yes, Friends). These six friends live in New York and are planning a trip to London. Various expenses will occur as they prepare for this trip: flights, hotel rooms, sightseeing tours, tickets for shows, and much more.
But here’s the twist:
There’s no one person administrating these accounts. Each friend has their own laptop, and they independently notify each other of their expenditures, who is sharing in those expenditures, and how much. For example, Joey might book the flights, Ross might get tickets to a museum, while Monica handles the hotel reservations. They each specify who’s sharing these costs.
The challenge: Devise a system that will allow each person to know, at any given time, how much they owe or are owed by their friends—without needing an administrator to track everything manually. The system should be able to handle all kinds of expenditures, as well as the percentages or amounts being shared.
Part 1:
Pause and think about how you would set that up in Excel. Remember, the system should allow notifications of spends independently, and all six friends should be able to see who owes how much and who is owed how much at any time during the trip, as well as when they settle the accounts at the end.
Take a moment to think, and then come back.
Welcome back! How did you get on with that?
Hang on to your solution, because we’re about to make things more interesting.
Part 2: Scaling It Up
This TV show Friends has become so popular that their group has expanded—dozens, even hundreds of people now want to join as friends of the friends. The system you’ve built? It needs to scale.
Instead of six friends, we’re talking about 60, 600, or even more people, and they could be spread across the world, not just in New York. It’s no longer just one trip to London; these friends are going on various trips and sharing costs continuously, forever.
The challenge is still the same: expenditures are notified independently, and each friend (or friend of the friends) must be able to see who owes them money or who they owe, at any given time.
Question: Will the system you designed handle this expansion? If not, how would you modify it to cope with hundreds of participants and ongoing expenses? Would you need to scrap it and start from scratch, or could it be adapted?
Pause again, think about that, and then come back.
Welcome back again!
Part 3: Preventing Joey’s Cheating (!)
Here’s the next twist: we have to consider safeguards. What’s stopping someone (like Joey, perhaps) from charging other people for things they didn’t agree to? For example, Joey could book a $500 dinner and try to split it with the others without their consent.
How do you ensure that any person being charged has actually agreed to share the cost? Can the system handle confirmations or approvals before anyone is billed? This becomes especially important when the group grows from a close-knit six to potentially thousands of friends.
What ideas do you have to implement these safeguards?
Take your time to think about it.
Welcome back, for the final time in this challenge.
Creative Thinking with Excel
If you’re wondering whether this is solvable or not, rest assured that a solution exists—and you will see it in the next part.
What you’ll learn in the next part is not only the solution but also the power of creative thinking with Excel. The truth is, these kinds of problems may seem overwhelming, but with some ingenuity, they can be solved in surprisingly simple ways.
Stay tuned, because in the next part, we’ll show you how it’s done, and you’ll be able to try it out for yourself.
Thank you for participating in this challenge. Keep thinking creatively!
This is a podcast by Hiran de Silva. Narrated by Charlie.
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