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[Numbers]: Rethink/Redesign Second Round #3299
Description
We're opening this issue to address problems with our two Numbers concept exercises, Currency Exchange and Electric Bill.
The Challenge: Come up with something better
- The exercise files in the repo: Currency Exchange & Electric Bill
- Refer to this issue for all the details on the problems with Currency Exchange.
- See this PR and this design.md for some detail on redesign choices made for Electric Bill.
- See this forum post for some of the feedback for Electric Bill.
- See this revisions list for the numbers
about.md, to get a feel for changes that have been made to the numbers concept over time.
Please use this issue to propose rewrites | restructuring | changes in story to one or the other of these exercises, along with any revisions you'd make to the numbers concept itself. Feel free to link to a PR for these suggestions. Keep in mind the PR will be auto-closed, but we will reopen any PRs that propose solid solutions to our issues. Our ultimate goal is to get either or both exercises to a state where we can all be comfortable / happy with them as numbers concept exercises for the track.
We don't want suggestions on re-working our concept tree or how teach math. We are also very aware of typos, mistakes, and spelling errors. While correcting them is important, that's not what we want here
Instead, we'd like to know what you would do to fulfill the requirements of writing this numbers concept exercise in a way that doesn't raise significant complaints, create confusion for students on the Python track, and is consistent with the intent of concept exercises, and their requirements. Keep in mind that this is the 2nd or 3rd exercise for the track, and many features of Python cannot be used at this stage, including other modules, loops, comprehensions, lists, tuples, sets, and so forth.
We are also not (at this time) interested in copying another tracks exercise, story or concept. We're interested is solving the issues with what we currently have.
Thank you very much for your ideas and support! 🌟
Activity
[-][Numbers]: Rethink/Redesign Number Two[/-][+][Numbers]: Rethink/Redesign Second Round[/+]3aluw commentedon Aug 15, 2025
Hello, I have some suggestions to improve the exchange machine exercise. Would you prefer that I share them here or on the forum?
BethanyG commentedon Aug 15, 2025
Hi @3aluw,
Thanks for asking. 🙂 (and for wanting to give feedback on an exercise!)
Whichever place you are most comfortable with. We recommend the forum, because you'll get more visibility and feedback from other track maintainers and students. But I'm fine with you putting your ideas here.
You can also put your ideas here & link to this issue in the forum.
3aluw commentedon Aug 16, 2025
Hello;
I was planning to post this in the forum, but I wasn’t sure which section would be the most appropriate. So, I’ll write it here for now, and once you let me know the right place to post, I can link it there as well.
This exercise is designed to introduce Python's number operations
introduction
using only very simple, real-world math (the kind learned in primary school).
Why?
since this could be the 2nd or 3rd topic in their learning journey.
The previous version of the Numbers exercise mixed many operations at once
and introduced complexity that distracted from learning Python syntax.
This version takes a more gradual, beginner-friendly approach by:
Progression of concepts covered:
+and-) – starting with simple calculations and service fees./) – figuring out how many bills are needed.%) – finding leftover change when amounts aren’t exact multiples.*) – scaling amounts for currency conversion.3aluw commentedon Aug 16, 2025
Currency Exchange 💰
Follow Chandler through his day at the currency exchange machine.
Each step introduces a new function you need to create.
1. Estimate value after exchange
Context:
Chandler starts by exchanging USD for EUR. On this day, 1 USD = 1 EUR.
However, the machine charges 1 USD as a service fee and displays the EUR amount as a float.
Task:
Create the
exchange_money()function, taking 1 parameter:value: The amount of USD Chandler wants to exchange.This function should return the EUR amount after subtracting the service fee.
Example:
2. Calculate number of 10 EUR bills
Context:
Chandler now wants to insert exact amounts using 10 EUR bills.
The machine still takes 1 EUR fee, so the calculation should be done after deducting the fee.
Task:
Create the
get_number_of_10_bills()function, taking 1 parameter:value: The amount of EUR Chandler wants to exchange.This function should return the number of 10 EUR bills Chandler will insert (don't forget 1$ fee).
Example:
3. Calculate change for non-multiples of 20
Context:
The machine only exchanges amounts that are multiples of 20 EUR.
Any remainder is returned as change.
Task:
Create the
get_change()function, taking 1 parameter:value: The amount of EUR Chandler wants to exchange.This function should return the change amount the machine gives back.
Example:
4. Convert EUR to Yen
Context:
Chandler decides to exchange his EUR for Japanese Yen.
The exchange rate is 1 EUR = 150 Yen.
Task:
Create the
exchange_to_yen()function, taking 1 parameter:value: The amount of EUR to be exchanged.This function should return the amount in Yen as a float.
Example:
5. Apply additional fee for less common currency pairs
Context:
The machine charges an extra 1.3% fee for exchanging less known pairs (like EUR/Yen)
Task:
Create the
apply_additional_fee()function, taking 1 parameter:amount: The amount in Yen before the extra fee.This function should return the final Yen amount Chandler gets after the fee is deducted.
Example:
BethanyG commentedon Aug 16, 2025
Hi @3aluw,
Thank you for your thoughtful comments and suggestions. I've created a forum thread for this under Python-->Programming. Hopefully others will chime in there. 😄
3aluw commentedon Aug 28, 2025
Hello @BethanyG,
since there haven’t been any negative comments on the suggested exercise, would it be okay if I go ahead and create a PR?