Sung has scored 99, 66, and 95 on his previous three tests. What score does he need on his next test so that his average (mean) is 83? How could I figure that out? help?

Question

whpalmer4 · Answer

Assuming the tests are all worth the same amount in his grade, here's what you are trying to solve:

The average of n items is just their sum, divided by n.  Let's let the score he needs on his next test be x.  Then we know that
$$\frac{99+66+95+x}{4} = 83$$
Solve that for x.

anonymous · Answer

is x 65?

whpalmer4 · Answer

My old math teacher used to say when anyone asked him such a question in an uncertain tone of voice: "is that an answer, or a prayer" :-)

anonymous · Answer

x is 72

whpalmer4 · Answer

There you go!

anonymous · Answer

thank you :)

whpalmer4 · Answer

And of course you can check that answer by putting it in place of x and verifying that the equality holds.

whpalmer4 · Answer

I'm of the general opinion that if it's worth doing the problem at all, it's worth checking your answer.