self Maths Puzzle

In Traffic signals, red flashes 3 times per minute and green flashes 5 times in 2 minutes at regular intervals.if both lights starts flashing at the same time, how many times do they flash together in each hour?

Read Solution (Total 2)

red flashes once for every 20seconds & green for every 24sec
LCM of 20&24 gives 120
so they flash together once for every 120 seconds i.e 2 mins
therefore in one hour ans is 30 times
11 years agoHelpfull: Yes(4) No(0)

edit:
red flashes once for every 20seconds & green for every 24sec
LCM of 20&24 gives 120
so they flash together once for every 120 seconds i.e 2 mins
therefore in one hour ans is 30 times
counting the first instant at 0th sec
total 31 times
11 years agoHelpfull: Yes(0) No(0)

self Other Question

(Y1,Y2,Y3,…,Y(n−1) ,Yn ) is a sequence of positive integers and n^2(Yn − Yn−1) − n(Yn + Yn−1). y1=y2=y3=1 . y50 ? On a journey across HYD, a taxi averages 30kmph for 60% of distance and 20kmph for 20% of diatance,and 10kmph for remainding.what is the average speed of whole journey?