Solve the problem.Scores on a test are approximately normally distributed with a mean of 70 and a standard deviation of 9. The teacher wants to give A's to the top 10% of students. What is the bottom cutoff for an A grade? Round your answer to the nearest whole number.
A. 79
B. 90
C. 80
D. 82
Answer: D
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Match the equation with the surface it defines.x2 + y2 = 81 
A. Figure 3 B. Figure 2 C. Figure 4 D. Figure 1
Solve the problem.Use the formula N = Iekt, where N is the number of items in terms of the initial population I, at time t, and k is the growth constant equal to the percent of growth per unit of time. A certain radioactive isotope has a half-life of approximately 1500 years. How many years would be required for a given amount of this isotope to decay to 25% of that amount?
A. 3000 years B. 2975 years C. 623 years D. 1125 years
Solve the problem.A vibrating wire has a vertical displacement given by 
Assume b and t are constants. Write y as a cosine function of x.
A. y = 6 cos(2?x + bt) B. y = cos(2?x - bt) C. y = 12 cos(2?x + bt) D. y = 6 cos(2?x - bt)
Subtract.8.62
A. 6.26 B. 7.16 C. 6.16 D. 7