Joe’s average (arithmetic mean) test score across 4 equally weighted tests was 35. He was allowed to drop his lowest score. After doing so, his average test score improved to 40. What is the lowest test score that was dropped?
Choose the correct choice from the following options:
A) 20	B) 25	C) 55	D) 65	E) 80

Rationale: the arithmetic mean of 4 equally weighted tests was 35 . so what we can assume is that we have 4 test scores , each 35 . he dropped his lowest score and the avg went to 40 . this means that the lowest score was not 35 and other three scores had given the lowest score 5 each to make it up to 35 too . when the lowest score was removed , the other 3 scores got their 5 back . so the lowest score was 3 * 5 = 15 less than 35 . so the lowest score = 35 - 15 = 20 answer ( a )
Answer: A