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Sep 16, 2013

# A traffic light at three different road crossing change

A traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively. If they change simultaneously at 7.00 a.m at what time will they change simultaneously again.?

Syeda

Member since Jan 25, 2017

Answer. Given that traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively. 48 = 2 × 2 × 2 × 2 × 3 72 = 2 × 2 × 2 × 3 × 3 108 = 2 × 2 × 3 × 3 × 3 Hence LCM of 48, 72 and 108 is (2 × 2 × 2 × 2 × 3 × 3 × 3)  = 432 That is after 432 seconds they will change simultaneously 432 seconds = 7 min 12 seconds Thus the traffic lights change simultaneously at 7:7:12 am SME Approved

Anmol Saket

Changing of traffic light at three different road=1st road=48 seconds                                                                   2nd road=72 seconds                                                                   3rd road=108 seconds LCM of 48, 72 & 108=2*2*3*2*2*3*3                              =432 seconds 432=432/60 minutes      =7 minutes 12 seconds. They will change simultaneously at 7:00 a.m + 7 minutes 12 seconds= 07:07:12 A.M. They will change simultaneously at 07:07:12 A.M.

Kishore Kumar

Given that traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively. 48 = 2 × 2 × 2 × 2 × 3 72 = 2 × 2 × 2 × 3 × 3 108 = 2 × 2 × 3 × 3 × 3 Hence LCM of 48, 72 and 108 is (2 × 2 × 2 × 2 × 3 × 3 × 3)  = 432 That is after 432 seconds they will change simultaneously 432 seconds = 7 min 12 seconds Thus the traffic lights change simultaneously at 7:7:12 am

Tejaswi

462

Ayush Singh

Given that traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively. 48 = 2 Ã 2 Ã 2 Ã 2 Ã 3 72 = 2 Ã 2 Ã 2 Ã 3 Ã 3 108 = 2 Ã 2 Ã 3 Ã 3 Ã 3 Hence LCM of 48, 72 and 108 is (2 Ã 2 Ã 2 Ã 2 Ã 3 Ã 3 Ã 3) = 432 That is after 432 seconds they will change simultaneously 432 seconds = 7 min 12 seconds Thus the traffic lights change simultaneously at 7:7:12 am
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