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Lori solved this multiplication problem:

[tex]\(29 \times 31 = 699\)[/tex]

Identify the mistake Lori made:

A. She didn't place a 0 in the ones column before multiplying [tex]\(3 \times 9\)[/tex].
B. She didn't multiply 3 and 9 correctly.
C. She didn't add after multiplying the multiplicand by 1 and 3.
D. She didn't regroup the 2 in the tens column.


Sagot :

Lori made a mistake in her multiplication, and we will address what she did wrong and correct it step-by-step:

### Step-by-Step Correction for [tex]\( 29 \times 31 \)[/tex]:

1. Multiplication of the ones' place of the multiplier:
- The multiplier is 31, so we first multiply the 1 in the ones' place (rightmost digit) by each digit of the multiplicand (29).

[tex]\[ 29 \times 1 = 29 \][/tex]

We write this down as the first partial product:

[tex]\[ \quad \ \ 29 \][/tex]

2. Multiplication of the tens' place of the multiplier:
- Next, we multiply the 3 in the tens' place by each digit of the multiplicand (29). Before we do this, we must place a 0 in the ones' place to indicate we are multiplying by the tens place (effectively 30).

[tex]\[ \begin{array}{r} \quad \ 29 \\ + \underline{(29 \times 30)} \end{array} \][/tex]

- Now, performing the multiplication:

- [tex]\(9 \times 3 = 27\)[/tex], write down 7 and carry over 2.
- [tex]\(2 \times 3 = 6\)[/tex], add the carried over 2: [tex]\(6 + 2 = 8\)[/tex].

Therefore, the second partial product is:

[tex]\[ 87 \quad \text{(Place the 0 in the ones' column and then write 87)} \][/tex]

3. Arrange and Add the Partial Products:
Now, add the two partial products together:

[tex]\[ \begin{array}{r} \ \ 29 \\ + 870 \\ \hline \ \ 899 \end{array} \][/tex]

So, the correct result should be [tex]\(899\)[/tex] for the multiplication [tex]\(29 \times 31\)[/tex].