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 evaluate each part separately and then add the results.

First, let's calculate 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, let's calculate 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:

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

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