Steve has these score on the exams for this semester: 89, 92, and 87. How much will have to make on the fourth exam to have a final average of an A (a 92% or better)?
A. 100%
B. 98% or better
C. 96% or better
D. 90% or better

I think it's D.

Question

Steve has these score on the exams for this semester: 89, 92, and 87. How much will have to make on the fourth exam to have a final average of an A (a 92% or better)?
	A.	100%
	B.	98% or better
	C.	96% or better
	D.	90% or better

I think it's D.

jamesj · Answer

If the score in the 4th exam is X, what is the mathematical expression for the average of the four scores?

jamesj · Answer

Suppose you have four scores: A,B,C and D.  
What is the mathematical expression for the average of those four numbers?

jamesj · Answer

The average of A,B,C and D is
$$ \frac{A+B+C+D}{4} $$
That being the case, what is the average of 89, 92, 87 and X ?

The point of writing that down is we want an algebraic way to find out what X has to be so the average is 92.

jamesj · Answer

@robtobey, it's really not so helpful to give the answer.  The question is why is that the right answer?  

I'm clearly trying to get KJ to think through the problem to arrive at the answer.  That way she can solve the problem herself, learn something and have the satisfaction of having found the answer.

So in other words, next time you see me or someone else trying to teach someone, please don't the process by just throwing out the answer.  Thanks.