Carcass wrote:
In the addition problem below, which of the following could be the digit C if A and B can be the same number?
\(2A7\)
\(B1\)
\(+C6\)
______
\(424\)
I. 1
II. 2
III. 3
(A) I only
(B) II only
(C) III only
(D) II and III
(E) I and III
Look at the Hundreds digit first - it is 4 = 2 + 2
This means A + B + C = 22, right?
No - we must also look at the ones digit - it is 4
Since, 7 + 1 + 6 is 14 - 1 gets carried to Tens digit
Thus A + B + C + 1 must be 22
i.e. A + B + C = 21
C = 21 - 2A (As, A = B)
Plug A = 9 (single digit numbers only)
C = 3
Plug A = 8
C = 5
Plug A = 7
C = 7
We see, on decreasing the value of A or B, C is increasing
The only match we have here is 3
Hence, option C