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Lori solved this multiplication problem:
[tex]\[ 29 \times 31 = 699 \][/tex]

However, the mistake Lori made when multiplying is that she didn't:
A. regroup the 2 in the tens column.
B. place a 0 in the ones column before multiplying [tex]$3 \times 9$[/tex].
C. multiply 3 and 9 correctly.
D. add correctly after multiplying the multiplicand by 1 and 3.


Sagot :

Alright Lori, let's carefully solve this multiplication problem step by step.

We need to calculate [tex]\(29 \times 31\)[/tex].

### Step-by-Step Multiplication:

1. Break down each number by place value:
- [tex]\(29\)[/tex] can be seen as [tex]\(20 + 9\)[/tex]
- [tex]\(31\)[/tex] can be seen as [tex]\(30 + 1\)[/tex]

2. Multiply each part separately:
- First, multiply [tex]\(9\)[/tex] by [tex]\(1\)[/tex]:
[tex]\[ 9 \times 1 = 9 \][/tex]

- Then, multiply [tex]\(9\)[/tex] by [tex]\(3\)[/tex] (which represents 30 because it’s in the tens place):
[tex]\[ 9 \times 3 = 27 \][/tex]
Here, we have to remember to regroup the 2 (which means you carry over the 2 tens).

3. Now, consider the [tex]\(20\)[/tex] (2 in the tens place):
- Multiply [tex]\(2\)[/tex] by [tex]\(1\)[/tex]:
[tex]\[ 2 \times 1 = 2 \][/tex]

- Then, multiply [tex]\(2\)[/tex] by [tex]\(3\)[/tex] (again, representing 30):
[tex]\[ 2 \times 3 = 6 \][/tex]
After regrouping the 2 from the previous multiplication (9*3), this becomes:
[tex]\[ 6 + 2 = 8 \][/tex]

4. Add the results together with correct placement:
- Our partial results are: 9, 27, 2, and 8.

5. Summarize the steps with correct place value:
We compute:
[tex]\[ 29 \times 31 = (9 + 270 + 20 + 60) = 899 \][/tex]

Thus, Lori's mistake was not properly regrouping the 2 and providing the correct sum. The correct answer is 899, not 699.