Final answer:
To calculate the grams of cocoa in Carmen's chocolate bar, multiply the weight of the bar (99 grams) by the cocoa percentage (31%). The result is 30.69 grams, which is rounded to the nearest tenth, resulting in 30.7 grams of cocoa.
Step-by-step explanation:
The question asks us to calculate the amount of cocoa in a chocolate bar based on its cocoa content percentage and total weight. To find out the amount of cocoa, we multiply the total weight of the chocolate bar by the percentage of cocoa it contains. Since we know that Carmen's chocolate bar is 31% cocoa and the weight of the chocolate bar is 99 grams, we perform the following calculation: 0.31 (31% as a decimal) × 99 grams = 30.69 grams.
Next, as instructed, we need to round our answer to the tenths place. The number 30.69 grams rounded to the nearest tenth is 30.7 grams. Hence, Carmen's chocolate bar contains 30.7 grams of cocoa when rounded to the tenths place as required.