, how long did the drive to the store take?

Question

A car drives to the store at a rate of 15 mph. On the drive home, the car averages 35 mph. If the total driving time is 2 hours, how long did the drive to the store take?

Answer 1

For home to store

 

speed = 15 mph

time =t

distance =x

 

speed =distance / time

15 =x/t

x=15t   ---------eq 1

For return journey(store to home)

 

speed = 35 mph

time =2-t

distance= x

 

35 =x/(2-t)

x=35(2-t)   ------------eq 2

 

now equate eq 1 and eq 2

 

15t = 35(2-t)

 

15t = 70-35t

 

50t =70

 

t=1.4

 

substitute t=1.4 eq 1

 

x= 15t

x= 15(1.4)= 21 miles

 

distance from home to store = 21miles