Problema Solution
If Stan has a course average score between 80 and 89, he will earn a grade of a B inn his algebra class. Suppose that he has four exam scores of 78, 69, 92 and 81 and that his teacher said that the final exam score has twice the weight of each of the other exams. What range of scores on the final exam will result in Stan earning a grade of a B?
Answer provided by our tutors
we assume that the phrase "between 80 and 89" is inclusive of 80 and inclusive of 89
four exams scores plus one exam worth two scores, so the final average is based on six exams
let 'x' represent the grade on the final exam, then we require that the average value fall between 80 and 89
80 <= (78+69+92+81+2x)/6 <= 89
80 <= (2(x+160)/6) <= 89
80 <= (x+160)/3 <= 89
240 <= x+160 <= 287
80 <= x <= 107
Stan can score between 80 and 107 on the final exam to earn a grade of B