Question

Traffic lights at three different road crossings change after 24 seconds, 36 seconds and 54 seconds, respectively. If they all change simultaneously at 10:15:00 a.m., then at what time will they change simultaneously again? `

• A. 10:18:36 a.m.
• B. 10:32:36 a.m.
• C. 12:03:00 a.m.
• D. 01:03:00 p.m.

Answer 1

Answer:

A. 10:18:36 a.m.

They all change simultaneously at 10:15:00 a.m They all change simultaneously again in, LCM ( 24 seconds, 36 seconds and 54 seconds ) = LCM (24, 36, 54) = 216 seconds = 3 minutes 36 seconds They all change simultaneously again in 3 minutes 36 seconds =10:15:00 a.m + 00:03:36 = 10:18:36a.m.