### Home > INT3 > Chapter 6 > Lesson 6.2.2 > Problem6-47

6-47.

Daylight Saving Time was adopted in the U.S. in 1918. During the oil crisis of the 1970s, the Department of Transportation found that Daylight Saving Time decreased national energy usage by about $1$ percent compared with standard time. Since then, not only has energy use in the U.S. changed but Daylight Saving Time has also been extended. In 2007 a group of researchers found that Daylight Saving Time decreased national energy usage by $0.2\%$ with a margin of error of $1.5\%$. If a $1\%$ decrease in energy use will save the state of Indiana $\9$ million, what conclusion(s) can you draw from the 2007 study in relation to the state of Indiana?

Energy usage can be expected to change in Indiana by $0.2\%$ $\pm1.5\%$.
What range of percentages is this? Use this range to calculate the cost/savings to the state.

Energy usage will change by $-1.3\%$ to $1.7\%$. Indiana could save up to $\11.7$ million, but could end up spending $\15.3$ million.