A recent survey of 400 pet owners reveals that the ratio of cat owners to dog owners is 4 to 5. If there are 500 registered cat owners , how many dog owners are there?
cat:dog=4:5
500=4 units
divide by 4
1 unit=125
5 unit=dog owners
125=1 unit
times 5 both sides
625=5unit=dog owners
625 dog owners