Three lights blink every 4.2 min, 5.6 min, and 8.4 min. When will they blink together again ?
16.8 min
Write each interval as a fraction with a common denominator: \(4.2 = \frac{42}{10}, \ 5.6 = \frac{56}{10}, \ 8.4 = \frac{84}{10}\).
The LCM of fractions is found using \(\text{LCM} = \frac{\text{LCM of numerators}}{\text{HCF of denominators}}\).
The LCM of 42, 56, and 84 is \(168\), and the HCF of the denominators (all 10) is 10.
\(\text{LCM} = \frac{168}{10} = 16.8\)
Hence, the lights will blink together again after 16.8 minutes.
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