Question

During one month, a homeowner used 600 units of electricity and 100 units of gas for a total cost of 390. The next month, 400 units of electricity and 250 units of gas were used for a total cost of $326. Find the cost per unit of gas.

Answer 1

$0.36

Explanation:

Let the cost per unit of electricity = e

Let the cost per unit of gas = g

a homeowner used 600 units of electricity and 100 units of gas for a total cost of 390;

600e + 100g = 390 ----- i

400 units of electricity and 250 units of gas were used for a total cost of $326.

400e + 250g = 326 ----- ii

Now we have two equations, and we solve for g;

600e + 100g = 390 ----- i

400e + 250g = 326 ----- ii

Multiply equation i by 4 and equation ii by 6;

2400e + 400g = 1560 ---- iii

2400e + 1500g = 1956 ---- iv

Subtract equation iii from iv;

1100g = 396

g =
`(396)/(1100)` = 0.36

Cost per unit of gas $0.36