Q:

Using Functions to Converting miles to kilometers

i am newbie and am trying to solve this function question in python:
This function converts miles to kilometers (km). Complete the function by having it return the result, then call the function to convert 55 miles, and print "The distance in kilometers is " with the result of the function. Then calculate the round-trip in kilometers by doubling it, and print "The round-trip in kilometers is " with that number. 
so far my code looks like this:
def convert_distance(miles):
km = miles * 1.6  # approximately 1.6 km in 1 mile
return km
miles = (55)    
km = convert_distance(miles)
print("The distance in kilometers is: " + str(km))
print("The round-trip in kilometers is: " + str(km * 2)) 

Anytime i try submitting it gives me this message pops-up:
Not quite. Remember to use the str() function to convert
numbers into strings when printing them with text, and to
call the function with just one parameter, then accept the
return value into a new variable.

A:

def convert_distance(miles):
    km = miles * 1.6 
    return km
result = convert_distance(55)
print("The distance in Kilometers is " + str(result))
print("The round-trip in Kilometers is " + str(result*2))

