Final answer:
To calculate the number of jellybeans in the jar, the mass of the empty jar was subtracted from the total mass, and then the mass of 20 jellybeans was used to find out the number of jellybeans per gram. Through division, we found that there are approximately 2890 jellybeans in the jar, which does not match any of the given options.
Step-by-step explanation:
To find out how many jellybeans are in the jar, we first need to determine the mass of just the jellybeans without the jar. We are given the mass of the jar with jellybeans as 1642 grams and the mass of the empty jar as 495 grams. By subtracting the mass of the jar from the total mass, we get:
Mass of jellybeans only = 1642 grams - 495 grams = 1147 grams
Next, we know that 20 jellybeans have a mass of 7.94 grams. To find out how many jellybeans make up 1147 grams, we can divide the total mass of the jellybeans by the mass of 20 jellybeans:
Number of jellybeans = 1147 grams / (7.94 grams / 20 jellybeans)
Number of jellybeans = 1147 grams / 0.397 grams per jellybean
Number of jellybeans ≈ 2890 jellybeans
None of the provided options (A. 74, B. 78, C. 82, D. 86) match the calculated answer. This suggests there might be a typo or misunderstanding in the options provided. The correct approach, however, to find the number of jellybeans is as explained above.