Question

During one month, a homeowner used 300 units of electricity and 120 units of gas for a total cost of $114.00. The next month, 290 units of electricity and 150 units of gas were used for a total cost of $115.30. Find the cost per unit of gas.

$_____

Answer 1

• $0.15

Explanation:

• Cost of electricity = x
• Cost of gas = y

Based on the given, we have equations:

• 300x + 120y = 114
• 290x + 150y = 115.30

Multiply the first equation by 29 and the second one by 30, then subtract the first equation from the second:

• 30*(290x) - 29(300x) + 30(150y) - 29(120y) =30(115.3) - 29(114)
• 4500y - 3480y = 153
• 1020y = 153
• y = 153/1020
• y = 0.15

The cost per unit of gas is $0.15