O-level Mathematics june 05 paper 1 questn 10

[dasani]

(10) Green Line buses run every 10 minutes.
Red Line buses run every 20 minutes.
Purple Line buses run every 35 minutes.
One bus from each Line leaves the city centre at 09 00.
After how many minutes will buses from all three Lines next leave the city centre at the same time?

 

[JaWaD]

Take there LCM
2 ! 10,20,35
2 ! 5,10,35
5 ! 5,5,35
7 ! 1,1,7
- ! 1,1,1

L.C.M = 2x2x5x7 = 140

So, after 140 minutes the three lines will again leave at the same time.

 

[dasani]

thanks