Final answer:
To find the grams of cocoa in Carmen's chocolate bar, multiply the weight of the chocolate bar by the percentage of cocoa (42%). The chocolate bar contains approximately 29.8 grams of cocoa.
Step-by-step explanation:
To find the grams of cocoa in Carmen's chocolate bar, we multiply the weight of the chocolate bar by the percentage of cocoa, which is 42%.
So, 71 grams x 42% = 29.82 grams of cocoa.
Rounding to the nearest tenth, we get 29.8 grams.