Question

At 1000 hours an aircraft starts from A to fly to B, a flight which will take 4 hours. At 1042 a second aircraft starts the same journey and will complete the flight in 2 hours 30 minutes. If the distance from A to B is 800 miles, at what time will the aircraft be the same distance from B?

Answer 1

when the distance between the 2 planes = 0 then they are the same distance from pointB

Answer 2

800/4 is the speed of the 1st aircraft

800/(2.5) is the speed of the second aircraft..

Answer 3

200 mph and 320 mph sound about right...

Answer 4

does 1042 means 42 minutes after 10?

Answer 5

yeah I got the speeds

Answer 6

thats right 45 mins after 10

Answer 7

ok, so if we convert 45 minutes into a fraction of an hour, we will be able to work with it better.... 3/4 or .75 of an hour....

Answer 8

42 mins*

but thats where I got stuck

Answer 9

ok... 60/42 is a good enough fraction to work with :)

Answer 10

yeah got that

Answer 11

divide each by 3... 20/14....10/7....

15/7 seems good... you agree?

Answer 12

10/7 seems good

Answer 13

yeah 10/7 looks ok

Answer 14

these are the options given:

a 1110 hrs
b 1124 hrs
c 1142 hrs
d 1152 hrs

Answer 15

lets make some equations then...

200x + 10/7 = D

320x = D

does that make sense to you?

Answer 16

I think i missed it... we need to know hoe far the first plane has traveled and add that...not the hours...lol

Answer 17

200(10/7) is the "added" distance, or the advantage that the 1st plane has...

Answer 18

ermm .. Y would it be + 10/7. Dont get how the + comes into it

Answer 19

ok that makes sense

Answer 20

200x + 285.7 = D

320x = D

where D is the equal distance flown .... hows that?

Answer 21

yeah that makes sense

Answer 22

makes better sense, but what doesnt make sense to me yet is that it is less than an hour, but the 1st plane has gone more than 200? gotta see where I missed that at :)

Answer 23

hmm ...

Answer 24

200(60/42) = 190.5 looks alot better, musta got it turned around in me head somewhere :)

Answer 25

I didnt get 190.5

Answer 26

7/10 should be our multiplier... 60 is the whole, 42 is the part; part/whole = percent.... .7

Answer 27

200(.7)= 140... that HAS to be it lol maybe

Answer 28

One way to consider it:

Look at the time when only the first is flying; it is going to 200mph for 42 minutes, so will end up 140miles away from A.

NEXT, look at the motion after they are both moving. If you apply a vector of -200mph to both planes, the one that set off first is effectively stationary, so you only need to consider how long it takes the second plane to 'catch up' the 140 mile head start at (320 - 200)mph = 120mph, which is just time = distance over speed. Add the initial 42 minutes and you're done.

Answer 29

200/60 tells us miles per minute; times 42 equals distance traved in 42 minutes...

Answer 30

200x+140 = 320x
140 = 320x - 200x

140 = 120x

x = 140/120 = 14/12 = 7/6...

1 hour and 6/60 minutes.... if it agrees with Newtons :)

Answer 31

oh that make sense
so it should be 200(42/60) = 140 (I.e the distances travelled by plane A)

Answer 32

Yep....

1042 + 0106 = 1148...

Answer 33

but these are the options:

a 1110 hrs
b 1124 hrs
c 1142 hrs
d 1152 hrs

Answer 34

1 hour and 1/6 of another .... ack!! my math is off today...

Answer 35

1hour and 10 minutes... double check that :)

Answer 36

1042+0110 = 1152....

Answer 37

But yes, I agree. Time = 42 minutes + (140/120) minutes = 42 + (7/6) hours = the same as yours.

Answer 38

Ahh .. thanks you