9. Bus A arrives every 12 minutes and Bus B arrives every 15 minutes. Both buses arrive together at 9am, what time do they next arrive together

Question

asked Jun 22, 2023 216k views

1 Answer

Kgutteridge · Answer 1 · 2023-06-29T01:15:27+0000

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Step-by-step explanation:

12 = 3*4

15 = 3*5

The GCF of 12 and 15 is 3

LCM of x and y = (x*y)/(GCF of x and y)

LCM of 12 and 15 = (12*15)/(GCF of 12 and 15)

LCM of 12 and 15 = (12*15)/(3)

LCM of 12 and 15 = 60

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We can confirm this by listing out the multiples of each

multiples of 12 are: 12, 24, 36, 48, 60, 72, ...

multiples of 15 are: 15, 30, 45, 60, 75, ...

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Since the LCM is 60, this means their schedules line up every 60 minutes, aka 1 hour.

If they arrive together at 9 AM, then their next arrival time together is 10 AM which is the final answer.