Cars, Assemble!
Cars, Assemble!

Cars, Assemble!

Learning Exercise



There are two different types of numbers in F#:

  • Integers: numbers with no digits behind the decimal separator (whole numbers). Examples are -6, 0, 1, 25, 976 and 500000.
  • Floating-point numbers: numbers with zero or more digits behind the decimal separator. Examples are -2.4, 0.1, 3.14, 16.984025 and 1024.0.

The two most common numeric types in F# are int and float. An int is a 32-bit integer and a float is a 64-bit floating-point number.

Arithmetic is done using the standard arithmetic operators. Numbers can be compared using the standard numeric comparison operators and the equality (=) and inequality (<>) operators.

Converting between number types is done through built-in conversion operators. These conversion operators are named after the type they will be converting to. F# does not support automatic conversion between number types.


The most common way to conditionally execute code in F# is by using an if/elif/else expression:

if x = 5 then
    printfn "Expression to evaluate when x equals 5"
elif x > 7 then
    printfn "Expression to evaluate when x greater than 7"
    printfn "Expression to evaluate in all other cases"

The condition(s) used in an if/elif/else expression must be of type bool. F# has no concept of truthy values.


In this exercise you'll be writing code to analyze the production of an assembly line in a car factory. The assembly line's speed can range from 0 (off) to 10 (maximum).

At its lowest speed (1), 221 cars are produced each hour. The production increases linearly with the speed. So with the speed set to 4, it should produce 4 * 221 = 884 cars per hour. However, higher speeds increase the likelihood that faulty cars are produced, which then have to be discarded. The following table shows how speed influences the success rate:

  • 0: 0% success rate.
  • 1 to 4: 100% success rate.
  • 5 to 8: 90% success rate.
  • 9: 80% success rate.
  • 10: 77% success rate.

You have three tasks.

1. Calculate the success rate

Implement the successRate function to calculate the success rate based on the production speed:

successRate 6
// => 0.9

2. Calculate the production rate per hour

Implement the productionRatePerHour function to calculate the assembly line's production rate per hour, taking into account its success rate:

productionRatePerHour 6
// => 1193.4

Note that the value returned is a float.

3. Calculate the number of working items produced per minute

Implement the workingItemsPerMinute function to calculate how many working cars are produced per minute:

workingItemsPerMinute 6
// => 19

Note that the value returned is an int.

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