There are 5 miles to 8 km. How many km in 80 miles?

Write a direct proportion to compare miles to Km.

#5/8 = 80/x" "(larr " miles")/(larr" km")#

You could decide what #5# was multiplied by to give #80# and do the same to the #8.#

#5/8xx 16/16 = 80/128" "(larr " miles")/(larr" km")#

Or Cross multiply to get:

#5x = 8xx80#

#x =(8xx80)/5#

#x= 128# km

OR Find a conversion factor:

#5 " miles " = 8 km#

#1 " mile " = 8/5 km#

#80 " miles " = 80 xx8/5 = 128 km#