College Physics (7th Edition)

$a). (3)\, less \,than\, 190\, mi/hr$ $b). 187.3mi/hr.$
a).Average speed will be (3) less than 190 mi/hr. Since, average speed is (Total distance travelled / Total time taken), it will be less than just the average of the speeds. b). Total distance = $2.5 \times 4= 10 mi$ Total time = $(\frac{2.5}{160}+\frac{2.5}{180}+\frac{2.5}{200}+\frac{2.5}{220}) hrs.$ So, Average speed =$\frac{Total \,distance}{Total\, time}=187.3 mi/hr$