One bottle of shampoo costs $6 for 8 ounces. A second bottle costs $4 for 5 ounces of shampoo. How much cheaper is the cheapest shampoo?

1) $6 for 8 ounces

Value per ounce = 6/8 = 0.75

You are paying $0.75 per ounce of shampoo.

2) $4 for 5

Value per ounce = 4/5 = 0.80

You are paying $0.80 per ounce of shampoo.

Comparing both value per ounce: (0.75 < 0.80)

You are paying more when using second bottle.

Bottle one is cheaper.

0.80 - 0.75 = 0.05

You are paying $0.05 more for bottle two.