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one bus leaves a stop every 9 minutes a second bus leaves every 15 minutes if they both leave at 1:25 at what time will they next leave together show work

Verified Answer :

In this question you need to find the lowest common multiple. I like to
do it the factor tree way:

15
9


/   \
/ \

3    5
3   3

See how there are both a 3 in the 15 factor tree
and there is at least on three in the 9 factor tree. So when you find the LCM,
you combine the two threes from the different factor trees like this:

3 x 5 x 3 = 45

So every 45 minutes the bus would be at the bus
stop together


Now simply add the 45mins onto the 1:25 

Answer: 2:10  

9 = 3^
15 = 3 x 5

both of them have 3, but take the bigger one ( 3^ )
LCM = 3^ x 5 = 45 min

1 : 25 + 0 : 45 = 2 : 10