Problem Solving

Q1
a and b are integers such that a/b =3.45. If R is the remainder of a/b, which of the following could NOT be equal to R?

a) 3 b)9 c)36 d)81 E)144

I understand how to derive the equation to 20 X R = 9 X b.

Lost on how the correct answer is a) (3).

Q2
When 15 is divided by y, the remainder is y - 3. If Y must be an integer, what are all the
possible values of y?

Understand the remainder,y, must be at least 3 and y at most can only be 18.

From this point you could pick numbers, dividing 15 by these numbers to check to see whether the
remainder is 3 lower than the number you have picked. Only 15 divided by 3,6,9, and 18 yield remainders
three less than the divisor:
15 = (5 x3) + 0
15 = (2 x 6) + 3
15 = (1 x 9) + 6
15 = (0 x 18) + 15

Remainder of 0 is 3 less than divisor of 3.
Remainder of 3 is 3 less than divisor of 6.
Remainder of 6 is 3 less than divisor of 9.
Remainder of 15 is 3 less than divisor of 18.


answer is 3,6,9,18. Still dont understand.

Please explain.

Thanks and regards

Charles