Traffic lights at three different road crossing change after 48 sec,72sec and 108 sec respectively. At what time will they change together again if they change simultaneously at 7 A.M.? (with full statement )
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We have to find the Lcm of 48sec, 72 sec, 108sec
48 = 2 × 2 × 2 × 2 × 3
72 = 2 × 2 × 2 × 3 × 3
108 = 2 × 2 × 3 × 3 × 3
LCM of 48, 72 and 108 is
2 × 2 × 2 × 2 × 3 × 3 × 3 = 432
after 432 seconds they will change simultaneously
432 seconds = 432/60 = 7 min 12 seconds
Thus the traffic lights change simultaneously at 7:7:12 am
48 = 2 × 2 × 2 × 2 × 3
72 = 2 × 2 × 2 × 3 × 3
108 = 2 × 2 × 3 × 3 × 3
LCM of 48, 72 and 108 is
2 × 2 × 2 × 2 × 3 × 3 × 3 = 432
after 432 seconds they will change simultaneously
432 seconds = 432/60 = 7 min 12 seconds
Thus the traffic lights change simultaneously at 7:7:12 am
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