Question

Two cars that are 150 miles apart start driving toward each other on parallel roads. The average speed of the first car is 60 miles per hour. The average speed of the second car is 55 miles per hour. Which equation can be used to determine t, the time it takes for the two cars to pass each other?

Answer 1

$<b > 60t + 55t = 150$

Answer 2

Solution-

Distance between the cars = 150 miles

Speed of the first car = 60 mph

Speed of the second car = 55 mph

Relative speed or net speed = 60+55 = 115 mph

( ∵ Relative speed is defined as the speed of a moving object with respect to another.

• When two objects are moving in the same direction, relative speed is calculated as their difference.
• When the two objects are moving in opposite directions, relative speed is computed by adding the two speeds. )

We know that,

$Relative\ Speed=\frac{Distance}{Time}$

$\Rightarrow Time=\frac{Distance}{Relative\ Speed}$

Putting the values,

$\Rightarrow t=\frac{150}{115}$

$\Rightarrow t=1.304\ hours$