In a coconut grove, (x + 1) trees yield 60 nuts per year, x trees yield 120 nuts per year and (x – 1) trees yield 180 nuts per year. If the average yield per year per tree be 100, find x.  Choices
A) 2	B) 4	C) 5	D) 6	E) none of the above

Rationale: "( x + 1 ) × 60 + x × 120 + ( x − 1 ) × 180 / ( x + 1 ) + x + ( x − 1 ) = 100 ⇒ 360 x − 120 / 3 x = 100 ⇒ 60 x = 120 ⇒ x = 2 answer a"
Answer: A