math
posted by missy on .
I don not understand how to do least common mutiples.
Can I please get some help.
I need to find the least common multiple of 420 and 196.
there is a real neat way to do this which works for the LCM of any number of numerals.
420 196
 divide each number by a common factor
105 49  4
15...7.} 7
there are no more common factors
so the LCM is the multiplation of the numbers on the far right as well as the last row
so LCM = 4 x 7 x 15 x 7 2940
if you had more than 3 numbers to start with there was a common factor for only some of them, take it out until there is no common factor for any
e.g.
400 250 230
200 125 215  2
40..25 43... 5
8....5 43... 5
so LCM = 2x5x5x8x5x43

43