1. Find Time Question(?)

Three bus services operate from the same depot.
The first service leaves at 10 minute intervals, the second at 15 minute
intervals and the third at 25 minute intervals.
All three services leave the depot together at 0800.
Find the time when the three services next leave the depot together.

How to solve such question?
I'm so weak in counting time.

2. Originally Posted by kismyjacq
Three bus services operate from the same depot.
The first service leaves at 10 minute intervals, the second at 15 minute
intervals and the third at 25 minute intervals.
All three services leave the depot together at 0800.
Find the time when the three services next leave the depot together.

How to solve such question?
I'm so weak in counting time.
You have to calculate the least common multiple of 10, 15 and 25:

$\displaystyle lcm(10, 15, 25) = 150$

Use prime number factorisation:

$\displaystyle 10 = 2 \cdot 5$
$\displaystyle 15 = 3 \cdot 5$
$\displaystyle 25 = 5\cdot 5$

Therefore $\displaystyle lcm(10, 15, 25) = 2\cdot 3 \cdot 5 \cdot 5 = 150$

3. Thanks

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three buses services operate from the same depot. the first service leaves at 10 mins interval, the second at 15 min and the third at

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