(b) \( 3,89 \times 4,21 \)

Let’s break it down a bit! Multiplying 3.89 by 4.21 gives us approximately 16.3789. You can visualize this by thinking of it like combining two fractions or even portions of a delicious pie—the more friends you have (the bigger the numbers), the more pie everyone gets! Now, if you want to perform this multiplication without a calculator, try setting it up like a regular long multiplication with whole numbers first, then adjust for the decimals at the end. Just remember to count how many total decimal places were in your original numbers and move the decimal point accordingly in your final answer!