In a certain month, the electricity consumption of a family's residence was 400 kWh. Thinking that the bill was high, the family members decided to reduce it and set a goal to decrease consumption by 40%. They started by replacing the refrigerator, which had a monthly consumption of 90 kWh, with another one that consumes 54 kWh per month. They also made some changes in the household routine: they reduced the shower time of the residents, saving 30 kWh per month; decreased the time the iron is on, saving 14 kWh per month; reduced the number of lights on during the night, achieving a reduction of 10 kWh per month. However, they realized that they would not reach the established goal and would need to decide on other ways to reduce energy consumption. In order to achieve this goal, the monthly energy consumption in kilowatt-hours still needs to decrease.

Mathematics

First, we need to calculate 40% of 400 kWh, which is the reduction goal. This gives us 160 kWh. Now, we add up the savings the family has already made: 90 - 54 (refrigerator) + 30 (shower) + 14 (iron) + 10 (lights) = 90 kWh. Then, we subtract the total saved from the reduction goal: 160 - 90 = 70 kWh. Therefore, the family still needs to reduce consumption by 70 kWh to reach the goal.

Question about Data Interpretation

Subject Mathematics

Mathematics

Source ENEM

ENEM

Topic Data Interpretation

Data Interpretation

Difficulty Hard

Hard

(ENEM 2021) - Question Hard of Mathematics