Question 39077
LCM OF 10,20 AND 35
LEAST COMMON MULTIPLE ..THAT IS THE SMALLEST NUMBER WHICH IS DIVISIBLE BY ALL THE 3 ABOVE NUMBERS .ONE METHOD IS TO BREAK THESE NUMBERS IN TO THEIR PRIME FACTORS.THAT IS 
TAKE 10...ITS FACTORS ARE 2*5
10=2*5.....................................I..SIMILARLY
20=2*2*5...............................II
35=5*7............................III
NOW TO GET LCM ,WE LOOK FOR COMMON FACTORS IN ATLEAST 2 OF THE ABOVE EQNS.I,II,III
WE FIND ONE 2 IS COMMON IN I&II
AND ONE 5 IS COMMON IN I,II,III
SO WE TAKE  THOSE COMMON FACTORS,LIST THEM  AND FIND THEIR PRODUCT..
LIST OF COMMON FACTORS....
2 AND 5.
THEIR PRODUCT =PCF(PRODUCT OF COMMON FACTORS)
2*5=10............................................IV
NOW WE  STRIKE OUT THE COMMON FACTORS AND WE LIST THE REMAINING 
NONE IN I(AS ONE 2 AND ONE 5 ARE LISTED IN COMMON FACTORS)
2 IN II (AS ONLY ONE 2 AND ONE 5 ARE LISTED IN COMMON FACTORS)
7 IN III(AS ONLY ONE 5 IS LISTED IN COMMON FACTORS)
SO LIST OF NON COMMON FACTORS..
2 AND 7
THEIR PRODUCT = PNCF
2*7=14............................................V
NOW LCM IS GIVEN BY PRODUCT OF COMMON ANF NON COMMON FACTORS..IV AND V.
LCM=10*14=140..