Bunuel wrote:

Dan had an average of 72 on his first four math tests. After taking the next test, his average dropped to 70. Which of the following is his most recent test grade?

(A) 60

(B) 62

(C) 64

(D) 66

(E) 68

Let the score in the fifth test be x

\(\frac{72*4 + x}{5} = 70\) --> x = \(350 - 72*4 = 350 - 288 = 62\)

Therefore, Dan would have scored a

62(Option B) in his fifth test to score an average of 70.

Shortcut: In the first four tests, he scores \(2*4 = 8\) more than the average.

In the last test, he would have scored {average - extra score} = \(70 - 8 = 62\) in order to average 70 overall!

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