Tính nhanh: B = 1 × 2 × 3 ... 10 + 10 × 11 × 12 × 13 × 14 × 15

To solve the expression \( B = 1 \times 2 \times 3 \times \ldots \times 10 + 10 \times 11 \times 12 \times 13 \times 14 \times 15 \), we need to break it down into two parts and compute each part separately.

First, we compute the product \( 1 \times 2 \times 3 \times \ldots \times 10 \). This is the factorial of 10, denoted as \( 10! \).

\[
10! = 10 \times 9 \times 8 \times 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 = 3,628,800
\]

Next, we compute the product \( 10 \times 11 \times 12 \times 13 \times 14 \times 15 \).

\[
10 \times 11 = 110
\]
\[
110 \times 12 = 1,320
\]
\[
1,320 \times 13 = 17,160
\]
\[
17,160 \times 14 = 240,240
\]
\[
240,240 \times 15 = 3,603,600
\]

Now, we add the two results together:

\[
B = 10! + 10 \times 11 \times 12 \times 13 \times 14 \times 15 = 3,628,800 + 3,603,600 = 7,232,400
\]

Thus, the value of \( B \) is \( 7,232,400 \).