I need help with these 2 word problems. Anyone? I appreciate "hints"? Thanks?

Question

Trains A and B are traveling in the same direction on parallel tracks. Train A is traveling at 40 miles per hour and train B is traveling at 48 miles per hour. Train A passes a station at 8:15pm. If train B passes the same station at 8:45pm, at what time will train B catch up to train A?

One more please.

In 1993, the life expectancy of males in a certain country was 72.6. In 1998, it was 75.8 years. Let E represent the life expectancy in year t and let t represent the number of years since 1993.

E(t)=____t+____ (Round the the nearest tenth)

Use the function to predict the life expectancy of males in 2006?

E(13)=_____ (Round to the nearest tenth)

Answer 1

1st question:

Use 60mph and 60 minutes as your base for almost every problem like this...So, that would mean A is 30 miles ahead of B. However, B is going 8mph faster. 8 mph divided into 30 miles equals 3.75 hours. 3.75 hours added on to 8:45pm equals 12:30a.m.

Question #2: I came up with 81.2...Not sure if I did it right though.

Answer 2

Train A speed = 40 miles/hour

Train B speed = 48 miles/hour

Train A passes a station at 8:15pm.

Train B passes that station at 8:45pm (30 minutes later = 0.5 hours)

So when Train B is passing the station, Train A is 40mph*0.5hours = 20 miles ahead.

Using 8:45pm as our point of reference, when train B catches up to train A, they both will have travelled the same distance from the station.

Therefore,

train A distance = 20 miles ahead + 40mph * T

train B distance = 48mph * T

train A distance = train B distance

20 miles ahead + 40mph * T = 48mph * T

20 + 40T = 48T

20 = 48T - 40T

20 = 8T

T = 2.5 hours

So add 2.5 hours to 8:45pm and you get 11:15pm when train B passes train A.

Answer 3

when train B passes the station you can calculate how far A is ahead of it. Then you know the difference in their speed, just calculate how long it will take to go that distance at the net speed of B with respect to A.