John knows that his first 4 test grades were 84,79,82,88. Find John's grade on the fifth test if his average was 83.8

Answer: The fifth grade is 86

Step-by-step explanation:

Given that there are five grades, let the missing fifth grade be represented by x:

84 + 79 + 82 + 88 + x / 5 = 83.8

333 + x/5 = 83.8

Next, we cross multiply:

333 + x = 83.8 x 5

333 + x = 419

Subtract 333 from both sides of the equation to get the value of x

333 + x - 333 = 419 - 333

x = 86