Jackie has two summer jobs. She works as a tutor, which pays $12 per hour, and she works as a lifeguard, which pays $9.50 per hour. She can work no more than 20 hours per week, but she wants to earn at least $220 per week. Which of the following systems of inequalities represents this situation in terms of x and y, where x is the number of hours she tutors and y is the number of hours she works as a lifeguard?
A) 12x + 9.5y ≤ 220
x + y ≥ 20
B) 12x + 9.5y ≤ 220
x + y ≤ 20
C) 12x + 9.5y ≥ 220
x + y ≤ 20
D) 12x + 9.5y ≥ 220
x + y ≥ 20
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Unmanned spacecraft taking images of Jupiter’s moon Europa have found its surface to be very smooth with few meteorite craters. Europa’s surface ice shows evidence of being continually resmoothed and reshaped. Cracks, dark bands, and pressure ridges (created when water or slush is squeezed up between 2 slabs of ice) are commonly seen in images of the surface. Two scientists express their views as to whether the presence of a deep ocean beneath the surface is responsible for Europa’s surface features.
A deep ocean of liquid water exists on Europa. Jupiter's gravitational field produces tides within Europa that can cause heating of the subsurface to a point where liquid water can exist. The numerous cracks and dark bands in the surface ice closely resemble the appearance of thawing ice covering the polar oceans on Earth. Only a substantial amount of circulating liquid water can crack and rotate such large slabs of ice. The few meteorite craters that exist are shallow and have been
smoothed by liquid water that oozed up into the crater from the subsurface and then quickly froze.
Jupiter’s magnetic field, sweeping past Europa, would interact with the salty, deep ocean and produce a second magnetic field around Europa. The spacecraft has found evidence of this second magnetic field.
No deep, liquid water ocean exists on Europa. The heat generated by gravitational tides is quickly lost to space because of Europa’s small size, as shown by its very low surface temperature (–160°C). Many of the features on Europa’s surface resemble features created by flowing glaciers on Earth. Large amounts of liquid water are not required for the creation of these features. If a thin layer of ice below the surface is much warmer than the surface ice, it may be able to flow and cause cracking and movement of the surface ice. Few meteorite craters are observed because of Europa’s very thin atmosphere; surface ice continually sublimes (changes from solid to gas) into this atmosphere, quickly eroding and removing any craters that may have formed.
1. Which of the following best describes how the 2 scientists explain how craters are removed from Europa’s surface?
2. According to the information provided, which of the following descriptions of Europa would be accepted by both scientists?
3. With which of the following statements about the conditions on Europa or the evolution of Europa’s surface would both Scientist 1 and Scientist 2 most likely agree? The surface of Europa:
4. Which of the following statements about meteorite craters on Europa would be most consistent with both scientists’ views?
5. Scientist 2 explains that ice sublimes to water vapor and enters Europa’s atmosphere. If ultraviolet light then broke those water vapor molecules apart, which of the following gases would one most likely expect to find in Europa’s atmosphere as a result of this process?
6. Based on the information in Scientist 1’s view, which of the following materials must be present on Europa if a magnetic field is to be generated on Europa?
7. Assume Scientist 2’s view about the similarities between Europa’s surface features and flowing glaciers on Earth is correct. Based on this assumption and the information provided, Earth’s glaciers would be least likely to exhibit which of the following features?
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