The Student Room Group

Calculating the Intersection

Hi everyone,

Can anyone help me out with calculating the intersection point of two vehicles travelling between two cities at different speeds, one setting off 30 minutes later than the other?

Thanks!!! :smile:
Reply 1
post a photo of the problem
Reply 2
Original post by TeeEm
post a photo of the problem
Reply 3
Original post by tommmyd


speed of first car is 80 km/h
can you find the speed of the other car?
Reply 4
Original post by TeeEm
speed of first car is 80 km/h
can you find the speed of the other car?


75km/h
Reply 5
Original post by tommmyd
75km/h


sorry on the phone

correct.

next after 15 minutes A would have covered 20 km.
so by the time B starts the two cars will be 80 km apart...

Are you following so far?
Can you see what to do next?
Reply 6
Original post by TeeEm
sorry on the phone

correct.

next after 15 minutes A would have covered 20 km.
so by the time B starts the two cars will be 80 km apart...

Are you following so far?
Can you see what to do next?



Thank you... I understand that but I am not sure what to do next. :confused:
Reply 7
Original post by tommmyd
Thank you... I understand that but I am not sure what to do next. :confused:


Car A has speed 80
Car B has speed 75 (you correctly found this)

at 10.15 the cars are 80 km apart and moving towards each other ....

so every hour that goes by, the distance between them is "eaten" at the rate of (75 +80)= 155 km.

can you see what to do next?
Reply 8
Original post by TeeEm
Car A has speed 80
Car B has speed 75 (you correctly found this)

at 10.15 the cars are 80 km apart and moving towards each other ....

so every hour that goes by, the distance between them is "eaten" at the rate of (75 +80)= 155 km.

can you see what to do next?


So in 30 minutes time the cars will be 77.5km closer to each other (2.5km apart)?
Reply 9
Original post by tommmyd
So in 30 minutes time the cars will be 77.5km closer to each other (2.5km apart)?


dead correct

do the right arithmetical operation and you will find the time (it is not exact)

then use it to find the distance from A (do not forget to add the 20 km)
Reply 10
Original post by TeeEm
dead correct

do the right arithmetical operation and you will find the time (it is not exact)

then use it to find the distance from A (do not forget to add the 20 km)


Am I right in thinking the cars will cross at about 10:46? :s-smilie:
Reply 11
Original post by tommmyd
Am I right in thinking the cars will cross at about 10:46? :s-smilie:


30 min and 58 seconds after 10.15 when I did my calculations.

hope you followed it


PS what course is this problem for?
Reply 12
Original post by TeeEm
30 min and 58 seconds after 10.15 when I did my calculations.

hope you followed it


PS what course is this problem for?


MST124 an Open module.

Thanks a lot!!!
Reply 13
Original post by tommmyd
MST124 an Open module.

Thanks a lot!!!


all good

Quick Reply

Latest