The mean gas mileage for a hybrid car is 57mpg. suppose that the gasoline mileage is approx normally distributed with a standard deviation of 3.5mpg. what proportion of hybrids gets over 61mpg?

If you have a graphing calculator (such as a TI-84), you can use the normalcdf feature by clicking on the blue "2nd" button, then the "vars" button and then choice 2. Since you are finding the proportion of hybrids that get over 61 mpg, the lower bound is 61, the upper bound is infinity (you can type in 99999), the mean is 57, and the standard deviation is 3.5. So... normalcdf(61,99999,57,3.5) = .1265. This means that 12.65% of the hybrids get over 61 mpg.