A car travel 45 mph at 9:00 pm, then another car leave 30 minutes later at 65 mph. When will they meet?
- print Print
- list Cite
Expert Answers
calendarEducator since 2010
write12,551 answers
starTop subjects are Math, Science, and Business
The first car leaves at 9:00 at 45 mph and 30 minutes later another car leaves at 65 mph. Let us assume they travel at a uniform rate throughout the journey.
In 30 minutes the first car has traveled 22.5 miles. The difference between the velocities of the two cars is 65 - 45 = 20 mph.
The time taken by the second car to travel an extra 22.5 miles is 22.5/ 20 = 1.125 hours
1.125 hours = 67.5 minutes or 1 hour 7.5 minutes.
So the cars will meet 1 hour 7.5 minutes after the first has left.
The cars meet at 7.5 minutes past 10.
Related Questions
- A car travels for 40 min at 45 mph. Then travels 145 minutes at 70 mph. Find the total distance.
- 2 Educator Answers
- A car is traveling at 44 mph. How long will it take to travel 99 miles?
- 1 Educator Answer
- A car travels at 55 mph for 24 min. Then travels at 75 mph for 135 min. Find the total distance...
- 2 Educator Answers
- A car travels at a speed of 64 mph. What is the distance travelled after 150 minutes?
- 1 Educator Answer
- Johnny drove at 32 miles per hour for 30 minutes and at 48 miles per hour for 45 minutes. How far...
- 2 Educator Answers
calendarEducator since 2008
write3,662 answers
starTop subjects are Math, Science, and Social Sciences
Let the distance both cars travels before they meet is D.
The time need to for car 1 is T1
The car needed for car 2 is T2
But car 2 leaves 30 minutes ( 0.5 h) after car 1
==> T2 = T1 - 0.5 ..............(1)
Let us use the speed formula.
For the first car:
==> S1 = D/T1
==> 45 = D/T1
==> D= 45*T1..............(2)
For the second car:
s2 = D/T2
==> 65 = D/ (T1-0.5)
==> D= 65*(T1-0.5) ..............(3)
Now from (2) and (3) we have:
45*T1 = 65*(T1 - 0.5)
==> 45T1 = 65T1 - 65/2
==> 20T1 = 65/2
==> T1 = 65/2*20 = 13/8 hours= 1 5/8 hours
We will convert 5/8 hour to minutes.
==> 5/8 * 60 = 37.5 minutes
Then the time needed for car 1 to meet car 2 is 1:37.5
But car 1 leaves at 9:00 pm
==> 9:00 + 1:37.5 = 10:37.5
Then, the cars meets at 10:37.5 pm.