Can not be determined

We can write any number N divided by D with quotient Q and remainder R as,
N = R + QD
In this case n is divided by 15 and leaves a reamainder 1. So,
n= 1 + 15Q
we can rewrite this as,
n= 1 + 5*3Q
n= 1 + 5*(3Q)
Now look at 5*3Q, that is saying that in the expression, 5 is the divisor and 3Q is the quotient and 1 is the remainder.
Thus we can conclude that when n is divided by 5 it also leaves remainder 1 with quotient being 3 times the quotient when divided by 15.

for folks who dont like formulas


suppose we take all multiples of 15(and add 1 remainders to each)

16, 31, 46

and we divide each by 5. we get 1 remainder.