A boy was asked to find the LCM of 3,5,12 and some another number. But while calculating he wrote 21 instead of 12 and yet got the correct answer. What would be the forth number.

Question

goformit100 · Answer

@AcidRa1n

zzr0ck3r · Answer

5 does not divide 12
so 12 is not the least common multiple of 5 and any number...

goformit100 · Answer

okay

goformit100 · Answer

Don't Spam My Question^

anonymous · Answer

sorry didn't realize one message was spam.. But ok

goformit100 · Answer

@zzr0ck3r After calculation I got 28 is it correct ?

it was a Long Paper working.

zzr0ck3r · Answer

this question does not make sense to me
lcm mean least common multiple
that means that the lcm of the set {a,b,c,d} will be divisible by each number in the set
so the lcm of 3,5,12,some other number
must be divisible by each of these numbers
5 does not divide 12 so 12 cant be the lcm of this set....

goformit100 · Answer

Okay. Then what to do then ?

zzr0ck3r · Answer

no idea, the question does not make sense
$$lcm\{3,5,12\} = lcm\{3,5,3*2^2\}=3*5*4=60$$

zzr0ck3r · Answer

so no matter what number we add to the set, this is only going to get bigger or stay the same......