Petrolyn motor oil is a combination of natural oil and synthetic oil. it contains 7 liters of natural oil for every 5 liters of synthetic oil. if 355 liters of synthetic oil are used, how many liters of petrolyn oil will be made?

What we know:
Petrolyn motor oil is a combination of natural oil and synthetic oil. It contains 7 liters of natural oil for every 5 liters of synthetic oil.

What we need to find:
If 355 liters of synthetic oil are used, how many liters of petrolyn oil will be made?

Set up a proportion to find how much natural oil is used.
7L natural oil/5L synthetic oil = x/355 synthetic oil where x=natural oil
7/5=x/355
(5)(x)=(7)(355) cross multiplied
5x=2485 simplified
5/5x=2485/5 multiplicative inverse
x=497L

Now, add both synthetic oil and natural oil to find amount of petrolyn oil.

355 L synthetic oil + 497 L natural oil= 852 L of petrolyn oil