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The traffic lights at three different road crossings change after every $48$ seconds, $72$ seconds and $108$ seconds respectively. If they change simultaneously at $7$ a.m., at what time will they change together next?
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$LCM = 432$
i.e. $\frac{432}{60} = 7$ min $12$ sec.
$\Rightarrow$ traffic lights will change simultaneously again at $7 : 7 : 12$ a.m.
i.e. $\frac{432}{60} = 7$ min $12$ sec.
$\Rightarrow$ traffic lights will change simultaneously again at $7 : 7 : 12$ a.m.