Question

A boutique owner is mixing an 18-ounce batch of her custom salt scrub, which costs $3.40 per ounce to make. It is made up of a tropical oil blend with a cost of $7.95 per ounce and sea salt with a cost of $1.45 per ounce. How many ounces of each should be used to make this batch?
Write your answers as whole numbers or as decimals rounded to the nearest tenth.
ounces of tropical oil blend
ounces of sea salt

Answer 1

Let x = ounces of tropical oil. Then 18 − x = ounces of sea salt.

Cost equation: 7.95x + 1.45(18 − x) = 3.40(18).

7.95x + 26.10 − 1.45x = 61.20 → 6.50x = 35.10 → x = 5.4.

So:
5.4 ounces of tropical oil blend
12.6 ounces of sea salt