1. The problem is to multiply 521 by 300. 2. The formula for multiplication is simply $a \times b$, where $a=521$ and $b=300$. 3. Multiply the numbers: $521 \times 300$. 4. Calculate step-by-step: - Multiply 521 by 3: $521 \times 3 = 1563$. - Since 300 is $3 \times 100$, multiply 1563 by 100: $1563 \times 100 = 156300$. 5. Therefore, the product of 521 and 300 is $156300$. This means if you have 521 groups of 300 items, you have a total of 156300 items.