Lebron is taking Calculus for Management, a class in which four tests are given. To get an A, he must average at least a 90 on the four tests. He got scores 89,

Question

Lebron is taking Calculus for Management, a class in which four tests are given. To get an A, he must average at least a 90 on the four tests. He got scores 89, 93, and 87 on the first three tests. What is the least he could score on the last test to earn an A in the class? (Express your answer as an inequality)

Answer 1

Whenever a student read a problem that contains the word average (when average is the arithmetic mean) the student should write the formula average = sum / count.  In 99% of these problems 2 of the three are given.  In this case the average is to be 90 and the count is 4.  The sum is 89 + 93 + 87 + x.  Therefore 90 times 4 = 269 + x.  x = 91.

 

Method 2: Use 90 as the average.  The scores given are -1, +3, and -3.  The deviation from the average must be zero so the last number must be +1.  Therefore the last score is 91.