Bunuel wrote:
A demographic survey of 100 families in which two parents were present revealed that the average age, A, of the oldest child is 20 years less than 1/2 the sum of the ages of the two parents. If F represents the age of one parent and M the age of the other parent, then which of the following is equivalent to A ?
(A) (F + M - 20)/2
(B) (F + M)/2 + 20
(C) (F + M)/2 - 20
(D) F + M- 10
(E) F + M+ 10
We can create the following equation:
A = (1/2)(F + M) - 20 = (F + M)/2 - 20
Answer: C
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89% (00:58) correct 
