A different digit is inserted into each of the two boxes to make the equation

$$
 15.2+1.52+0.15 \square+\square .128=20
$$

true. The sum of the digits in the two boxes is
(A) 5
(B) 6
(C) 7
(D) 8
(E) 9

## Part B: Each correct answer is worth 6.
We rewrite the addition in columns, and write each number to three decimals:

$$
\begin{array}{r}
15.200 \\
1.520 \\
0.15 \square \\
+\square .128 \\
\hline 20.000
\end{array}
$$

Since the sum of the digits in the last column ends in a 0 , then the box in the thousandths column must represent a 2.

We can insert the 2 to get

15.200

1.520

0.152

$+\square .128$

20.000

If we then perform the addition of the last three columns, we will get a carry of 1 into the units column. Since the sum of the units column plus the carry ends in a 0 , then the box in the units column must represent a 3. Therefore, the sum of the digits inserted into the two boxes is 5. (We also check that $15.2+1.52+0.152+3.128=20$.)

## Part B