Statistics

Question

Your average grade after 5 tests in Biology is a 65. However, after the most recent test your average
increased to a 70. What grade did you get on the test in order to increase your average?

Answer 1

 

The first 5 grades were a, b, c, d, e (you don't need to know the first 5 grades in numbers to solve this problem)

 

So the first average is (a+b+c+d+e)/5 = 65

 

Then it comes the 6th grade f which is the unknown grade we need to solve our equation for

 

So the second average is (a+b+c+d+e+f)/6 = 70

 

We go back to the first average and note that a+b+c+d+e = 5*65 = 325

 

Substitute the value 325 into the second average and you get (325+f)/6 = 70 which I guess you know how to solve for f (easy!)