SOLUTIONLast year the average (arithmetic mean) salary of the 10 employees of Company X was $42,800. What is the average salary of the same 10 employees this year?Note that it's almost always better to express the average in terms of the sum.
Given: total salary is $42,800*10.
Question: new total salary=?
(1) For 8 of the 10 employees, this year's salary is 15 percent greater than last year's salary. Clearly insufficient.
(2) For 2 of the 10 employees, this year's salary is the same as last year's salary. Clearly insufficient.
(1)+(2) Consider two possible cases:
2 lowest salaries didn't change and 8 highest salaries increased by 15%;
2 highest salaries didn't change and 8 lowest salaries increased by 15%;
Ask yourself, would new total salary be the same for both cases? No, because the increase in amount for the first case will be greater than the increase in amount for the second case. Hence even taken together statements are not sufficient.
Hope it's clear.
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