PrepTest 123, Section 3, Question 2

What we’re looking for

Working the answers

• A
  Correct

  A smaller share of household gas use doesn't tell us why the bill increased. The bill depends on how much gas the household uses and what that gas costs, not on what percentage goes to one appliance.

  Imagine the old heater used 20 of the household's 100 units of gas. The new one uses 10 of the household's 100 units. Its share dropped from 20 percent to 10 percent, but total use stayed at 100 units. At the same rate, the bill would stay the same. Other totals could produce a higher bill or a lower one. The smaller percentage alone doesn't explain which happened.

  If A feels less obvious than the others, compare what each remaining choice actually adds. They give us extra demand for gas or a higher price. A gives us neither.

• B

  Now two people live there instead of one. Jimmy's uncle could add showers, dishes, and other hot-water use. A heater can be more efficient at heating a given amount of water while using more gas overall because it has much more water to heat. We don't need to assume the gas use exactly doubles; the extra person gives us a reason it could increase.

• C

  Jimmy has added another gas appliance. The new heater might save gas, but those savings could be outweighed by the gas used to dry his clothes. Before, that drying wasn't part of his household's gas consumption. This gives us a concrete reason for a higher bill.

• D

  Each unit of gas costs more. Even if the heater reduces the number of units Jimmy uses, the price increase could be large enough to make the total bill rise. A smaller quantity doesn't guarantee a lower total when the price changes.

• E

  Cold weather caused heavy gas use. That extra demand can raise the household's bill despite savings from a more efficient water heater. This fits the furnace possibility we considered while reading: the whole bill reflects more than the heater's efficiency.