GMAT - Problem Solving Aufgabe 3
Arithmetik, Algebra und Geometrie. Aus diesen Bereichen stammen die mathematischen Aufgaben beim GMAT.
Versuchen Sie, die folgende Aufgabe möglichst schnell zu lösen.
Jack, Tom, Beth an Ruth are each competing to paint one side of a square fence. The fastest, Jack, painted his side in 13 hours, the slowest, Tom, painted his side in 14 hours. Which of the following could NOT be the average of the times that each of the four competitors spent painting his or her side of the fence?
(A) 13.2
(B) 13.3
(C) 13.5
(D) 13.6
(E) 13.7
Lösung
The solution is obtained by testing the answer against the conditions specified in the problem. Suppose, the average time is 13.2. Then the total time to paint the fence is 13.2 x 4 = 52.8, which leaves only 25.8 (52.8 - 13 - 14 = 25.8) hours in total for Ruth an Beth to complete the task. So, each of them must do it in less than 13 hours, and this is impossible since the least time to paint a side is 13 hours. Therefore, the best answer is (A).
