Question 1045433
 A school has 20 teachers, one of them retires at the age of 60 years and a new teacher replaces him, this change reduces 
the average age of the staff by 2 years, the age of new teacher is: 
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Original average of the 20 teachers:: "a"
Sum of their ages = 20a
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After one retires::
Sum of the 19 teachers ages:: 20a-60
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Let the new teachers age be "t"
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Equation::
original average - new average age = 2 years
a - [20a-60+t]/20 = 2
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20a - 20a + 60 - t = 40
t = 20 yrs ( new teacher's age)
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Cheers,
Stan H.
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