Let distance between ลำปาง and เชียงใหม่ = d
then we can know the Velocity of ขบวนรพด่วนออกจากเชียงใหม่ =
d/(18-5) ===> d/3.
the Velocity of ขบวนรพด่วนออกจากลำปาง =
d/(18-13.5) ===> d/(4.5) .
let t = hours after 15.00
we can set up the equation
(d/3)t + (t+1.5)(d/4.5) = d
divine both sides by d
we will have
(t/3) + (t/4.5) + (1/3) = 1...solve for t
1.5t+t = (1.5)X2
2.5t = 3
t = 1.2 or 1 hour and 12 minutes
So รถทั้งสองคันนี้แล่นสวนกันเวลา 15.00 + 1.12 = 16.12 pm krab
Sorry I can't typein Thai... Cozz I live in USA
I just know this website a few days ago....
This website is so interesting for me
..Bye