Final answer:
Janice exchanges place-value blocks for 18 tenths and 12 hundredths when dividing 1.92 by 6 because it is easier to work with whole numbers in division, transforming the operation into dividing 192 hundredths by 6, resulting in 32 hundredths, or 0.32.
Step-by-step explanation:
Janice is dividing 1.92 by 6. In this process, she exchanges the place-value blocks for 18 tenths and 12 hundredths. This is because when dividing decimal numbers, especially in a concrete or pictorial format like place-value blocks, it's easier to work with whole numbers. So, by converting 1.92 into hundredths, she turns it into 192 hundredths. Dividing 192 hundredths by 6 gives 32 hundredths, or 0.32. This is equivalent to 3 tenths and 2 hundredths, or, in terms of place-value blocks, 18 tenths (since 3 tenths multiplied by 6 equals 18) and 12 hundredths (2 hundredths multiplied by 6 equals 12).