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
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