Mathematics for IGCSE & O level - Number (Section 1 - No. 43)
Two lighthouses flash at intervals of 22 seconds and 16 seconds, respectively. If they flash together at 10:00 PM, when will they next flash together?
10:02 PM
10:04 PM
10:06 PM
10:08 PM
Explanation
The problem requires finding the least common multiple (LCM) of 22 and 16. 22 = 2 x 11 and 16 = 2^4. LCM(22, 16) = 2^4 x 11 = 176 seconds = 2 minutes and 56 seconds. Therefore, the next time they flash together is 10:00 PM + 2 minutes and 56 seconds = 10:02 PM.
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