tutonaranjo wrote:Is the integer n a multiple of 15?
1) n is a multiple of 20
2) n + 6 is a multiple of 3
Answer is C. Appreciatte a detailed explanation.
To be divisible by 15 it must have factors 3 and 5
From 1 we know that n i divisble by 20 so it could be 20,40,80 or maybe 60
Thus n has factors 5 and 4 for sure and probably 3 but not known
From 2 we know that is divisble by 3 since (n+6)/3 = n/3 +6/3 and this is still a multiple
So n has a factor 3 for sure but we dont know if it has 5 as a factor.
Combining both, we get that n has factors 3, 4 and 5 thus ensuring that it is a multiple of 15
