There are only blue cubes, yellow cubes and green cubes in a bag. There are twice as many blue cubes as yellow cubes and five times as many green cubes as blue cubes. Sarah takes at random a cube from the bag. Work out the probability that Sarah takes a yellow cube. Give your answer in its simplest form.

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?