A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 40.0 min at 50.0 km/h, 8.0 min at 70.0 km/h, and 35.0 min at 35.0 km/h and spends 40.0 min eating lunch and buying gas. Determine the average sped for the trip. Determine the difference between the intial citties along the route.

Average speed = 40.50 km/h (Approx)

Explanation:

Distance = Time × Speed

Total distance = (40/60) 50 + (8/60) 70 + (35/60) 35

Total distance = 33.33 km + 9.33 km + 20.17 km

Total distance = 62.80 km

Average speed = Total distance / Total time taken

Average speed = 62.80 / [(40+8+35+40)/60]

Average speed = 62.80 / 1.55

Average speed = 40.50 km/h (Approx)

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form