Question

3 lightships flash simultaneously at 6 00

a.m. the first lightship flashes every 12 sec , the second lightship every 30 sec and the third lightship every 66 sec . at what time will the three lightships next flash together

Answer 1

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Start Time
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6.00am

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Find LCM of 12, 30, 66
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12 = 2² x 3
30 = 2 x 3 x 5
66 = 2 x 3 x 11
LCM = 2² x 3 x 5 x 11
LCM = 660

⇒ The 3 lights will flash simultaneously again 660 sec later

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Convert seconds to minutes
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660 sec = 11 min

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Calculate the next time the 3 lightships will flash simultaneously again
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6.00 am + 11 mins = 6.11 am

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Answer: The 3 lightships will flash at 6.11 am again
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