At Tampines Bus Interchange, Bus 8 leaves every 12 minutes and Bus 28 leaves every 18 minutes. They both leave together at 7:00 a.m. After how many MORE minutes will they next leave together?
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Worked Solution
Step 1: Recognise this as a "next time they coincide" problem → find the LCM of 12 and 18.
Step 2: List the multiples of each number until you find the first match. Multiples of 12: 12, 24, 36, 48, 60,... Multiples of 18: 18, 36, 54, 72,...
Step 3: The smallest number that appears in BOTH lists is 36. So LCM(12, 18) = 36.
Step 4: After 36 minutes, both buses will leave together again. Check: 36 ÷ 12 = 3 → Bus 8 has made 3 trips ✓. 36 ÷ 18 = 2 → Bus 28 has made 2 trips ✓. Answer: 36 minutes.
Answer: 36
Correct answer: 36
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