Question

The least common multiple of 20, 24, and 45 is _____.
a) 30
b) 180
c) 360
d) 21,600

Answer 1

Neither.

Answer 2

\[20 = 2 \cdot 2 \cdot 5\]\[24 = 2 \cdot 2\cdot 2 \cdot 3\]\[45 = 3\cdot 3\cdot5\]So, \(\rm lcm(20,24,45) = 2\cdot2\cdot 3 \cdot 5 \cdot 2 \cdot 3\)

Answer 3

@OneKoi: Hello?

Answer 4

360

Answer 5

If a simpler way is needed,\[\begin{array}{l|r} 5 & {20,24,45} \\ \hline 4 & 4,24,9 \\ \hline 3& 1,6,9 \\ \hline2 & 1,2,3 \\ \hline 3 & 1,1,3 \\\hline & 1,1,1 \end{array}\]

Answer 6

So, \(5 \cdot 4 \cdot 3 \cdot 2 \cdot 3 = \cdots \)

Answer 7

just an alternative method...
list out multiples for all of them..
like
20---->20,40,60,80......
24---->24,48,....
45---->....
and see which multiple comes out to be common first.
but its the crude(and easy) way to find, but long.

Answer 8

@OneKoi: Do you know any of the three methods listed?

Answer 9

@OneKoi is not in the room or in front of Computer I think...

Answer 10

Seems so...