# Hints

## General

## 1. Estimate value after exchange

- You can use the [division operator][division-operator] to get the value of exchanged currency.

## 2. Calculate currency left after an exchange

- You can use the [subtraction operator][subtraction-operator] to get the amount of change.

## 3. Calculate value of bills

- You can use the [multiplication operator][multiplication-operator] to get the value of bills.

## 4. Calculate number of bills

- You need to divide `amount` into `denomination`.
- To remove decimal places from a floating point value, you can use the [`floor()`][floor] function.
- You need an integer to get the exact number of bills.
 The `floor` function can take the desired output type as a parameter.

  **Note:** The [`÷` operator][div], or `div()` function, also does floor division. However, if an operand is floating point the result is still floating point.

## 5. Calculate leftover after exchanging into bills

- You need to find the remainder of `amount` that does not equal a whole `denomination`.
- The [Modulo operator][div] `%` can help find the remainder.

## 6. Calculate value after exchange

- You need to calculate `spread` percent of `exchange_rate` using multiplication operator and add it to `exchange_rate` to get the exchanged currency.
- The actual rate needs to be computed. Remember to add exchange _rate_ and exchange _fee_.
- You can get exchanged money affected by commission by using a divide operation, plus type casting to integer if necessary.

[division-operator]: https://docs.julialang.org/en/v1/manual/mathematical-operations/#Arithmetic-Operators
[multiplication-operator]: https://docs.julialang.org/en/v1/manual/mathematical-operations/#Arithmetic-Operators#Arithmetic-Operators
[subtraction-operator]: https://docs.julialang.org/en/v1/manual/mathematical-operations/#Arithmetic-Operators
[floor]: https://docs.julialang.org/en/v1/base/math/#Base.floor
[div]: https://benlauwens.github.io/ThinkJulia.jl/latest/book.html#_floor_division_and_modulus