In an examination the following scores were a chief by a group of students: draw a cumulative frequency graph of the data and use it to find:
a) The median examination mark.
b) How many students score less than 65 marks
c) How many students scored between 50 and 80 marks
d) How many students failed, given that the pass mark is 50
e) The credit mark, mark given that the top 25% of students were awarded credits
f) The interquartile range.
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Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.