Monday, August 13, 2012

What are the two natural no. whose difference is 66 and the least common multiple is 360?

Let the GCD be x

then 2 numbers are mx,nx: with out loss of generality let m > n

now LCM = mnx ( as m and n are copimes)

so difference = (m-n) x = 66

mnx = 360

now 11 does not devide x so 11 devides (m-n)

m-n = 11 => x = 6 so mn = 60

m-n = 11
mn = 60

can be solved to give m = 15, n= 4 so numbers are 90 and 24


if m-n = 22 then x= 3 and

so mn = 120 does not have integer solution

m-n = 33 => x = 2 so mn = 180 does not have integer solution

m-n = 66 => x = 1 so mn = 360 does not have integer solution

so only solution (90,24)

13 comments:

Unknown said...

now 11 does not devide x so 11 devides (m-n)
How can you say this . Please explain me.

kaliprasad said...

as (m-n) x = 66 and 11 divides 66 so it must divide x or m-n. so as 11 does not devide x so 11 divides (m-n)

Unknown said...

how can u say 11 does not divide x????

kaliprasad said...

as product mnx is 360 so 11 does not divide product of m , n and x and hence it does not divide x because if 11 divides x then it divides mnx or360.

Unknown said...

mister kali prasad , i am not getting one thing . yes i have understood till 11 divides (m-n). but i am not getting how
(m-n) = 11 and x = 6 . can u tell me the steps to get that , ( m-n) = 6 or how did you get that (m-n) = 6

Unknown said...

how is (m-n) = 11 and x = 6 . please tell me the method to get that i have understood till the above step , but i am not getting how (m-n)=11 and x=6 . please tell me the method how did you get that ?

kaliprasad said...

11 does not divide x because x divides 360 so 11 divides n-n. I never mentioned m -n = 6. what I mentioned is m-n is multiple of 11

Unknown said...

Why 11 has come into picture first?

kaliprasad said...

11 comes because it is factor of 66.
11 is not factor of mnx(which is 360) so not a factor of x

but it is a factor of (m-n) x = 66 so factor of m-n

Unknown said...

need to be simplified further

kaliprasad said...

it cannot be simplified further

Unknown said...

I cannot understand this solution

kaliprasad said...

which part you cannot understand