A rectangular garden is to be twice as long as it is wide. If 240 yards of fencing, including the gate, will completely enclose the garden, what will be the length of the garden, in yards?  Pick one
A) 40  B) 50  C) 60  D) 80  E) 100

Rationale: "alternate approach backsolving ( using answer options to reach the correct answer ) can work wonders here if one is fast in calculations . given perimeter is 240 so , 2 ( l + b ) = 240 or , l + b = 120 now use the answer options ( given length ; breath will be half the length ) ( a ) 40 l = 40 ; b = 20 l + b = 60 ( b ) 50 l = 50 ; b = 25 l + b = 75 ( c ) 60 l = 60 ; b = 30 l + b = 90 ( d ) 80 l = 80 ; b = 40 l + b = 120 ( e ) 100 l = 100 ; b = 50 l + b = 150 thus you see no , need of any calculations , u can reach the correct option only by checking options ; correct answer will be ( d )"
Answer: D