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Two bells ring at intervals of 9 and 15 minutes. They ring together at noon. When do they ring together again?
Aafter 9 min
Bafter 15 min
Cafter 30 min
Dafter 45 min
Answer & Solution
Correct answer: D. after 45 min
Meeting time = LCM(9, 15). 9 = 3², 15 = 3·5. LCM = 3²·5 = 45. They ring together again 45 min after noon.
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