11 Plus Exams Forum

This may sound very basic but still thought of posting

what is LCM of 3 & 9, is it 9 or 18

9

3 x 3 = 9
1 x 9 = 9

my answer is also 9
but it seems 18 is LCM of 3 and 9, this was told to my kid

3 6 9 12 15 18

9 18 27 36

hence 18

oxyeleven wrote:my answer is also 9
but it seems 18 is LCM of 3 and 9, this was told to my kid

3 6 9 12 15 18

9 18 27 36

hence 18

But in that example, the series still intersect at 9...?

yes answer is 9 to me also.

oxyeleven wrote:my answer is also 9
but it seems 18 is LCM of 3 and 9, this was told to my kid

3 6 9 12 15 18

9 18 27 36

hence 18

Wrong - it is 9 [Graduate mathematician and qualified teacher] - LOWEST common multiple

LCM means lowest common multiple
IF they asked what is the LCM of 3,9

Multiples of 3 are 3,6,9,12,15,18,21,24,27,30
Multiples of 9 are 9,18,27,36,45,54,63,72,81,90

Common multiples of 3,9 are 9,18,27,36,45,54,63,72,81,90

Among the common multiples what is the lowest common multiple of 3,9?..Answer is 9..
18 is a common multiple of 3,9 but not the lowest common multiple..

If there are two numbers A,B, A is a smaller number and B is a bigger number.
If A goes into B then the LCM of A,B is B

Examples : LCM of 3,15 answer is 15
Lcm of 4,16 Answer is 16...