Question

An athlete runs from A to B and comes back at a speed of 10 kmph, while a second athlete simultaneously runs from B to A and comes back at a speed of 15 kmph. If they cross each other for the first time in 12 minutes after they start, they will meet each other the second time in

Answer 1

Do you see how to find the distance between A and B?

Answer 2

speed in opposite directionis 10+15=25kmph
speed =dist/time,
time=d/25

Answer 3

so what's the distance between A and B?

Answer 4

120 km

Answer 5

10*12=120

Answer 6

reasonability check: if they are 120 km apart, are the two guys really going to meet after only 12 minutes of running?!?

Answer 7

dont know

Answer 8

come on, 120 km? do you normally use km or miles?

Answer 9

km

Answer 10

well, you said the speed is 25 km per hour. that means about 5 hours to cover the whole distance...

Answer 11

but these guys are supposed to cover the distance between A and B in 12 minutes!

Answer 12

look, between the 2 of them, they cover 25 km each hour. in 12 minutes (= 1/5 of an hour, because 12/60 = 1/5), they meet up. that means the distance between A and B must be 1/5 of 25 km, no?

Answer 13

10/12=5/6km,15/12=5/3km

Answer 14

5km

Answer 15

right!

Answer 16

second time 10km

Answer 17

how to calculate time then ?is it 24 min

Answer 18

the second meeting isn't quite as easy as that to find...

the two runners will cover 10km in 24 minutes, true. but the question is will they be at the same point at that time?

at the first meeting:
runner 1 will have run 12/60 * 10 = 2 km
runner 2 will have run 12/60 * 15 = 3 km

Answer 19

After another 12 minutes of running, runner 1 will have run 24/60 * 10 = 4 km and runner 2 will have run 24/60 * 15 = 6 km

Answer 20

That means runner 1 will be almost to B (4/5 of the way there), and runner 2 will have gotten to A and started back to B

Answer 21

they aren't in the same spot, so that isn't where they meet for the 2nd time

Answer 22

what about in another 1/5 hour of running?

Answer 23

after 60 minutes they meet?

Answer 24

after48 minutes

Answer 25

i think after 48 minutes only they meet

Answer 26

becoz a covered 8 km and b covered 12km

Answer 27

am i correct they will meet at 3km

Answer 28

do u understand @whpalmer4

Answer 29

I think they meet again at 3/5 of an hour. runner 1 will have done 3/5 * 10 = 6 km, runner 2 will have done 3/5 * 15 = 9 km.



runner 1 goes from A to B and 1 km back toward A. runner 2 goes from B to A and 4 km back toward B, ending up 1 km away from B, which is where runner 1 is.