Answer
1) The proportion of the number of times in which gas mileage was between 18 and 21 miles per gallon is 0.1107.
2) The probability that a randomly select gas mileage is between 18 and 21 miles per gallon is 0.1107.
Work Step by Step
1) $\frac{number~of~times~in~which~gas~mileage~was~between~18~and~21~miles~per~gallon}{total~number~of~observed~gas~mileage}=0.1107$
2) $P(18\lt X\lt21)=0.1107$
