If four different numbers are chosen from 5, 6, 7, 8, 9 to replace the $\square$ 's below, what is the smallest possible sum of the two 2-digit numbers?
(A) 123
(B) 125
(C) 126
(D) 134
(E) 161
To find the smallest possible sum, we first choose the tens digit of each number to be as small as possible.

Therefore, we choose 5 and 6 as the two tens digits.

Next, we choose the units digits to be as small as possible.

Since 7 and 8 are each less than 9 , we choose 7 and 8 as the two units digits.

Using 5 and 6 as the tens digits, 7 and 8 as the units digits, we evaluate the only two possibilities.

| 57 |
| ---: |
| $+\quad 68$ |
| 125 | | 58 |
| ---: |
| $\quad 125$ |

(Can you see why these two sums should be equal?)

The smallest possible sum is 125 .

ANSWER: (B)