Question 329717
THE 1 YOU FOUND WAS THE TIME NOT THE RATE.
D=RT
FOR THE EXPRESS TRAIN:
90=RT
THE LOCAL TRAIN:
90=R/3(T+2)
SET THESE 2 EQUATION EQUAL:
RT=R/3(T+2)
RT=(RT+2R)/3 CROSS MULTIPLY
3RT=RT+2R
3RT-RT=2R
2RT=2R CANCEL THE RS.
2T=T
T=1 HOUR.
90=R*1
90=R FOR THE EXPRESS TRAIN.
PROOF:
90/3=30 MPH FOR THE LOCAL
90=30(1+2)
90=30*3
90=90