The average age of 5 pupils is 11 years. When their teacher joins them, the average age becomes 15 years. How old is the teacher?
A30 years
B40 years
C26 years
D35 yearsCORRECT
Common EntranceMathematicsAverage
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Toaster Teacher
Why the answer is D, and why the others tempt you.
Total age of pupils = 5 x 11 = 55. Total with teacher = 6 x 15 = 90. Teacher = 90 - 55 = 35 years.
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