1st Car leaves point A at 5pm at avg speed of 80km/hr. Second car leaves point A 45 minutes later at 110km/hr. When does the 2nd car catch the 1st car. Show working.

Hi Kayla;

All of the above answers are great. However, when I took physics, this is the way we had to show all work.

The question is...

*1st Car leaves point A at 5pm at avg speed of 80km/hr. Second car leaves point A 45 minutes later at 110km/hr. When does the 2nd car catch the 1st car.*

**Show working**.Emphasis supplied

As Justin explains,

*distance = rate x time*The question is when does the distance of 1st car=2nd car

(rate)(time)=(rate)(time)

x=time in hours of first car. (Note the specification of hours.)

(80 km/hr)(x)=(110 km/hr)(x-0.75hrs)

As part of

**showing all of your work**, this is your next step...(80 km/hr)(x)=(110 km/hr)(x-0.75)

The kilometers and hours cancel. You need to cancel words as much as you need to cancel numbers.

80x=110(x -0.75)

We must isolate x.

Let's spread-out...

80x=110x-82.5

Let's divide both sides by 80...

80x/80=(110x-82.5)/80

x=1.375x-1.03125

Let's subtract 1.375x from both sides...

x-1.375x=-1.375x-1.03125

-0.375x=-1.03125

Let's divide both sides by -0.375

(-0.375x)/(-0.375) = -1.03125/-0.375

x= 2.75

After 2.75 hours from the time of departure of the first car, the second car caught-up with the first car.

According to Kirill, this is 7:45 pm.