4. Calculate the following:

Example:

[tex]
\[
\begin{array}{l}
3432 \times 26 \\
\begin{array}{r}
3432 \\
\times \quad 26 \\
\hline
20592 \longrightarrow 6 \times 3432
\end{array} \\
=6 \times (3000+400+30+2) \\
=18000+2400+180+12 \\
=20592 \\
+68640 \longrightarrow 20 \times 3432 \\
=20 \times (3000+400+30+2) \\
=60000+8000+600+40 \\
=68640
\end{array}
\]
[/tex]

Problems:

a. [tex] 7382 \times 39 [/tex]

b. [tex] 6928 \times 72 [/tex]

Sure! Let's solve each multiplication step-by-step in detail.

### Part (a): [tex]$7382 \times 39$[/tex]

We can break down the multiplication into smaller, more manageable parts.

First, break 39 into two parts: 30 and 9.

1. [tex]$7382 \times 9$[/tex]

[tex]\[
7382 \times 9 = 66438
\][/tex]

2. [tex]$7382 \times 30$[/tex]

[tex]\[
7382 \times 30 = 221460
\][/tex]

Now, add these two results together to get the final answer:

[tex]\[
66438 + 221460 = 287898
\][/tex]

So, [tex]$7382 \times 39$[/tex] equals [tex]$287898$[/tex].

### Part (b): [tex]$6928 \times 72$[/tex]

Similar to part (a), we can break 72 into 70 and 2.

1. [tex]$6928 \times 2$[/tex]

[tex]\[
6928 \times 2 = 13856
\][/tex]

2. [tex]$6928 \times 70$[/tex]

[tex]\[
6928 \times 70 = 484960
\][/tex]

Now, add these two results together to get the final answer:

[tex]\[
13856 + 484960 = 498816
\][/tex]

So, [tex]$6928 \times 72$[/tex] equals [tex]$498816$[/tex].

### Summary

- Part (a): [tex]$7382 \times 39 = 287898$[/tex]
- Part (b): [tex]$6928 \times 72 = 498816$[/tex]

These are the detailed steps to find the answers for both parts of the question.