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Solution to the mortgage calculator challenge
class Mortgage
attr_reader :principal, :down_payment_percentage, :apr, :duration_in_years
def initialize(principal, down_payment_percentage, apr, years)
@principal = principal
@down_payment_percentage = down_payment_percentage
@apr = apr
@duration_in_years = years
end
def number_of_payments
duration_in_years * 12
end
def down_payment
down_payment_percentage * principal
end
def monthly_rate_decimal
(apr/12) / 100
end
def monthly_payment
# (monthly_rate_decimal * (principal - down_payment) ) / (1 - ((1 + monthly_rate_decimal) ** (-1 * number_of_payments)) )
amount_owed / payment_coefficient #Both of these calculations yield the monthly payment
end
def amount_owed
( (1 + monthly_rate_decimal) ** number_of_payments ) * (principal - down_payment)
end
def payment_coefficient
counter = 1
sum = 1
(number_of_payments.to_i - 1).times do
sum += (1 + monthly_rate_decimal) ** counter
counter += 1
end
sum
end
def principal_payment
(principal - down_payment) / number_of_payments
end
def total_interest_paid
(monthly_payment * number_of_payments) - principal
end
end
# require_relative 'mortgage'
DOWN_PAYMENT_PERCENTAGES = [0.05, 0.10, 0.15, 0.20]
print "What is the home value: "
home_value = gets.chomp.to_f
print "What is the APR: "
apr = gets.chomp.to_f
print "What is the duration (in years): "
duration_in_years = gets.chomp.to_f
puts
puts sprintf("%-15s %-10s %-10s %-20s %-20s",
"Down Payment", "Duration", "APR", "Monthly Payment", "Total Interest Paid")
DOWN_PAYMENT_PERCENTAGES.each do |down_payment_percentage|
mortgage = Mortgage.new(home_value, down_payment_percentage, apr, duration_in_years)
puts sprintf("%-15.2f %-10d %-10.3f %-20.2f %-20.2f",
mortgage.down_payment, duration_in_years, apr,
mortgage.monthly_payment, mortgage.total_interest_paid)
end
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