Answer:
The option A has the cheapest price of the liter, so it is the better buy.
Step-by-step explanation:
The best buy is going to be the one with the lowest liter price.
The liter price of each option can be found by a rule of three problem:
Rule of three problem:
In a rule of three problem, the first step is identifying the measures and how they are related, if their relationship is direct of inverse.
When the relationship between the measures is direct, as the value of one measure increases, the value of the other measure is going to increase too. In this case, the rule of three is a cross multiplication.
When the relationship between the measures is inverse, as the value of one measure increases, the value of the other measure will decrease. In this case, the rule of three is a line multiplication.
For each option, in this problem, the measures are:
- The number of liters bought
- The total cost
As the number of liters bought increases, so will the total cost. It means that the relationship between the measures is direct.
Option A:
2 liters - $1.29
1 liter - x
2x = 1.29
x = 0.645
In option A, each liter costs $0.645
Option B
A six pack of half a liter was bought. So in all, 3 liters were bought.
3 liters - $2.99
1 liter - x
3x = 2.99
x = $0.997
In option B, each liter costs $0.997
Option C
A 12 pack of half a 0.35 liter was bought. So in all, 4.2 liters were bought
4.2 liters - $3.50
1 liter - x
4.2x = 3.50
x = $0.8333
In option C, each liter costs $0.8333
The option A has the cheapest price of the liter, so it is the better buy.