16. Which is closest to \( 17.8 \times 9.9 \) ? a. 140 b. 180 c. 200 d. 350 e. 400

To estimate \( 17.8 \times 9.9 \), we can round the numbers to make the multiplication easier. Rounding \( 17.8 \) to \( 18 \) and \( 9.9 \) to \( 10 \), gives us \( 18 \times 10 = 180 \). Thus, the closest answer to \( 17.8 \times 9.9 \) is \( \text{b. 180} \). Now, let's calculate the exact value to confirm our estimation. Performing the multiplication \( 17.8 \times 9.9 \) yields \( 176.22 \), which is indeed closest to \( 180 \).