Freelancer Rates
Freelancer Rates

Freelancer Rates

Learning Exercise



There are two different kinds of numbers in Elixir - integers and floats.

Integers are whole numbers.

integer = 3
# => 3

Floating Point Numbers

Floats are numbers with one or more digits behind the decimal separator. They use the 64-bit double precision floating-point format.

float = 3.45
# => 3.45

Working with numbers

In the Integer and Float modules you can find some useful functions for working with those types. Basic arithmetic operators are defined in the Kernel module.


Integers and floats can be mixed together in a single arithmetic expression. Using a float in an expression ensures the result will be a float too.

2 * 3
# => 6

2 * 3.0
# => 6.0

However, when doing division, the result will always be a float, even if only integers are used.

6 / 2
# => 3.0

To convert a float to an integer, you can discard the decimal part with trunc/1.


In this exercise you'll be writing code to help a freelancer communicate with a project manager by providing a few utilities to quickly calculate daily and monthly rates, optionally with a given discount.

We first establish a few rules between the freelancer and the project manager:

  • The daily rate is 8 times the hourly rate.
  • A month has 22 billable days.

Sometimes, the freelancer is offering to apply a discount on their daily rate (for example for their most loyal customers or for non-for-profit customers).

Discounts are modeled as fractional numbers representing percentage, for example 25.0 (25%).

1. Calculate the daily rate given an hourly rate

Implement a function to calculate the daily rate given an hourly rate:

# => 480.0

The returned daily rate should be a float.

2. Calculate a discounted price

Implement a function to calculate the price after a discount.

FreelancerRates.apply_discount(150, 10)
# => 135.0

The returned value should always be a float, not rounded in any way.

3. Calculate the monthly rate, given an hourly rate and a discount

Implement a function to calculate the monthly rate, and apply a discount:

FreelancerRates.monthly_rate(77, 10.5)
# => 12130

The returned monthly rate should be rounded up (take the ceiling) to the nearest integer.

4. Calculate the number of workdays given a budget, hourly rate and discount

Implement a function that takes a budget, an hourly rate, and a discount, and calculates how many days of work that covers.

FreelancerRates.days_in_budget(20000, 80, 11.0)
# => 35.1

The returned number of days should be rounded down (take the floor) to one decimal place.

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