The area of a square field is A square feet and the perimeter is p feet. If 6A=6(2p+9), what is the perimeter of the field, in feet? (Here A=a^2)  Options
A) 28  B) 36  C) 40  D) 56  E) 84
You can also solve this via using the given numbers in the answer choices!   Of course you need to be aware of the basic properties as outlined by the other posts above (a = x^2 and p = 4x)   Starting with D you will notice that x=14 is way too big for your area (14^2) and will not satisfy: 6A=6(2p+9) or a=2p+9   --&gt; Eliminate D and E   Now pick 36 (its either too big, then its A, or too small then you know its C or it is 36 itsself)   And picking 36 indeed solves the problem! (36/4 --&gt; 9; a= 9^2 = 81 and 81=2x36+9)
<result>B</result>
The area of a square field is A square feet and the perimeter is p feet. If 6A=6(2p+9), what is the perimeter of the field, in feet? (Here A=a^2)