Question

A citizen decides to travel another city at 10:13 a.m. The citizen at 10:31 a.m. is stopped by a police officer when he has already traveled 20 miles. The agent gives the citizen a chance, but warns him to be careful and the citizen then slows down by 10 mi / h. Later the citizen arrives at his destination at 11:17 a.m. (a) Calculate the average speed of the citizen moving from city to city. (b) It typically takes a person in his car to travel the 42.9 mile between city and city in 48 min. How does this typical speed compare to the average speed of the citizen in part (a)? That is, the citizen is above or by. Below average typical speed.

Answer 1

(a)

average speed = total distance / total time taken

at 10:31 am , he was stopped and at 11:17 am , he reached the destination

in first 18 minutes, 10: 13 am to 10:31 am, he already did 20 miles means his speed was

speed = 20 / 0.3 = 66.66 miles/hr

then after being stopped, he slowed down by 10 mi/h

so, his new speed is 56.66 miles/hr

at this speed,

distance till 11:17 am

d = 56.666 * (46/60) = 43.444

so,

total distance = 20 + 43.44 = 63.44

total time = 10:13 a.m to 11:17 a.m = 64 min = 1.066 hr

so,

average speed = 63.44 / 1.066

average speed = 59.5 mi/h

_______________

(b)

for a typical person

average speed = 42.9 / 0.8 = 53.6 mi/h

this average speed is lower than average speed found in (a)