Teerex wrote:

If a and b are two-digit positive numbers and c is a three digit positive number, such that c=a+b. Is the unit digit of c the same as the unit digit of a?

1) All the digits of c are the same and all the digits of a are the same

2) The tens digit of a is the same as the tens digit of b

As \(c\) is sum of two-digit numbers so the hundred's digit of \(c\) will be \(1\) (max possible value \(99+99=198\))

Statement 1: implies \(c=111\). \(a\) cannot be \(11\) because in this case no value of \(b\) will add up to \(111\)

so for unit's digit of \(c\) to be \(1\), unit digit pairs of \(a\) & \(b\) can be (2,9),(3,8),(4,7),(5,6) etc.

Hence unit's digit of \(a\) is not equal to unit's digit of \(c\).

SufficientStatement 2: nothing mentioned about \(c\).

InsufficientOption

A