Question

Two planes travel toward each other from cities that are about 450 km apart at rates of 240 ​km/hr and 210 ​km/hr. They started at the same time. In how many hours will they​ meet?

Answer 1

1 hour.

Explanation:

You have to do the total distance /total speed together.

You have to do this to ensure that you are counting how fast they are travelling together.

(450 km) / the sum of their speed (240+210)

450/ (240+210)

=450/ 450

=1

Answer: 1 Hour.

Answer 2

t = 1 hour

Explanation:

Oddly the distances add. Each plane will contribute a certain distance to make the 450 km. They will meet after the same number of hours have passed.

d = r * t

r1 = 240 km/hour

t1 = t

r2 = 210 km/hour

t2 = t

240*t + 210*t = 450 collect the terms on the left.

450t = 450 divide by 450

450t/450 = 450/450

t =1

After 1 hour they will meet.