To solve this question quickly, first remove decimal by multiplying each term with 100,Then terms become 210, 105, 63Then HCF of above terms is 21, So Answer is 0.21
L.C.M. of 60 and 62 seconds is 1860 seconds1860/60 = 31 minutesThey will beep together at 10:31 a.m.Sometimes questions on red lights blinking comes in exam, which can be solved in the same way
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