Challenge 12 is all about calculating simple interest. It asks that the program prompt for the principal, the rate as a percentage, and the amount of time. This is also a useful program, and good for working with the math operators of your language. Once again, I used Ruby. The first time through this I didn’t use the Useful Methods file, so I went back and integrated that into the file:
require ‘../useful_methods.rb’
principal = getFloat(“Enter the principal”)
interest = getFloat(“Enter the percentage rate of interest (5% should be 5)”)
time = getFloat(“Enter the time in number of years”)
amount_accrued = principal * (1 + (interest / 100) * time)
puts “After %#.2f years at %#.2f%%, the investment will be worth $%#.2f.” % [time,interest,amount_accrued]
You’ll notice that I was able to use the odd syntax with the %#.2f and then have the individual numbers in an array after the string.
The follow-up challenges are to make a method called calculateSimpleInterest() instead of just running through it line by line, and to have it print out the amount of money accrued after each year. I addressed it in this way:
require ‘../useful_methods.rb’
def calculateSimpleInterest()
principal = getFloat(“Enter the principal”)
interest = getFloat(“Enter the percentage rate of interest (5% should be 5)”)
time = getFloat(“Enter the time in number of years”)
1.upto(time) do |time|
amount_accrued = principal * (1 + (interest / 100) * time)
puts “After %#.2f years at %#.2f%%, the investment will be worth $%#.2f.” % [time,interest,amount_accrued]
end
end
puts calculateSimpleInterest()
And the result is:
And that’s day 13 of 57!
Corbett Winningham 