Question

If the number 2345 a 60b is exactly divisible by 3 and 5, then the maximum value of a + b is
(a) 12
(b) 13
(c) 14
(d) 15

Answer 1

A number is divisible by 5 if its last digit is either 0 or 5 out of which 5 is maximum.
∴ b = 5
A number is divisible by 3 if the sum of its digits is divisible by 3
2 + 3 + 4 + 5 + 6 + 0 + 5 = 25
So, we can add maximum 8 to 25 which will give us 33 which is divisible by 3.
∴ a = 8
Now, a + b = 8 + 5 = 13
Hence, the correct answer is option (b).