Question 107382
There are two ways to go after this one.  The simple way is to recall that a right triangle with legs of 3 and 4 has a hypotenuse that measures 5. (3-4-5 right triangle).  3+4+5 = 12.


Or, if you don't recall the 3-4-5 right triangle, you can fall back on our good friend Pythagoras who said that the square on the hypotenuse is equal to the sum of the squares on the other two sides, or symbolically:


{{{c^2=a^2+b^2}}}, or in terms of c (the value we need to determine),


{{{c=sqrt(a^2+b^2)}}}


In this case:  {{{c=sqrt(3^2+4^2)=sqrt(9+16)+sqrt(25)=5}}}.


Again, our sides are 3, 4, and 5, so our perimeter must be 12.