The fuel efficiency (mpg rating) for cars has been increasing steadily since 1980. The formula for a car's fuel efficiency for a given year between 1980 and 1996 is E 0.36x + 15.9 where E is miles per gallon and z is the number of years after 1980. Note: Round your answers down to get the corresponding year. For instance, at 3.25, the year is 1983 . a. In what years was the average fuel efficiency for cars less than 17 mpg (in interval form)?
b. In what years was the average fuel efficiency for cars more than 20 mpg (in interval form)?

a) In the interval of [1980,1983].

b) In the interval of [1991, 1996].

Step-by-step explanation:

Fuel efficiency:

The fuel efficiency, for the cars, in x years after 1980, is given by:

15.9 is the fuel efficiency in 1980.

a. In what years was the average fuel efficiency for cars less than 17 mpg (in interval form)?

From 1980 to:

3.06 = 1980 + 3 = 1983. So

In the interval of [1980,1983].

b. In what years was the average fuel efficiency for cars more than 20 mpg (in interval form)?

From x until 1996.

11.38 = 1980 + 11 = 1991. So

In the interval of [1991, 1996].

"it's not the heat, it's the humidity".   that's a partly valid phrase you may have heard in the summer, but it's actually both.   the heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.   this has important considerations for the human body's comfort.   when the body gets too hot, it begins to perspire or sweat to cool itself off.   if the perspiration is not able to evaporate, the body cannot regulate its temperature.   evaporation is a cooling process.   when perspiration is evaporated off the body, it effectively reduces the body's temperature.   when the atmospheric moisture content (i.e. relative humidity) is high, the rate of perspiration from the body decreases.   in other words, the human body feels warmer in humid conditions.   the opposite is true when the relative humidity decreases because the rate of perspiration increases.   the body actually feels cooler in arid conditions.   there is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases).

step-by-step explanation: