Question

Help!!! Please

Math

A "Local" train leaves a station and runs at an average rate of 35 mph. An hour and a half later an "Express" train leaves the station and travels at an average rate of 56 mph on a parallel track. How many hours after the Express train starts will the it overtake the Local?


{ a0 hrs.}

Answer 1

Local say "L" is going at a speed of 35mph...ok... and Express or "X" is going at 56mph.

by the time the two trains meet, and X is ready to overtake L, the distance that both have travelled, since is a parallel road, is the same, say "d". So if L has travelled "d" miles, then X had travelled "d" miles too, over the same road, maybe different lane.

now, because X left 1 1/2 hour later, by the time they meet, say X has been running for "t" hours, but because it left 1 1/2 hour later, L has been running for " t + 1 1/2 " hours, or " t + 3/2 " hours.

Explanation:

so, they met 2 and a half hours later after X left, and a milllisecond later X overtook L.

Answer 2

2.5

Explanation:

Remark

The key to this problem is to list the givens. When you do, the problem becomes much easier.

Givens

For the "local" the givens are

t = t + 1.5 hours

d = the total distance d

r = 35 mph

For the Express the givens are

t = t hours

r = 56 miles per hour

d = the total distance this train has to travel

Note: The distance traveled for both trains is the same

Express distance = "local" distance

d = rt for both

56*t = 35*(t + 1.5) Remove the brackets

56*t = 35*t + 52.5 Subtract 35t from both sides.

56t - 35t = 52.5 Collect like terms

21t = 52.5 Divide both terms by 21

t = 52.5/21 Perform the division

t = 2.5 hours